String.LastIndexOf Метод

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(System::String ^ value, int startIndex, int count, StringComparison comparisonType);

public int LastIndexOf (string value, int startIndex, int count, StringComparison comparisonType);

member this.LastIndexOf : string * int * int * StringComparison -> int

Public Function LastIndexOf (value As String, startIndex As Integer, count As Integer, comparisonType As StringComparison) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение начального индекса параметра value, если эта строка найдена, или -1, если она не найдена или если текущий экземпляр равен Empty.

Исключения

Примеры

В следующем примере показаны три перегрузки метода LastIndexOf, которые находят последнее вхождение строки в другой строке с использованием различных значений перечисления StringComparison.

// This code example demonstrates the 
// System.String.LastIndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the last occurrence of a character using different " + 
                   "values of StringComparison.";
    string resultFmt = "Comparison: {0,-28} Location: {1,3}";

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string CapitalAWithRing = "\u00c5"; 

// Define a string to search. 
// The result of combining the characters LATIN SMALL LETTER A and COMBINING 
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
    string cat = "A Cheshire c" + "\u0061\u030a" + "t";
    int loc = 0;
    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

// Clear the screen and display an introduction.
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because culture affects the result. For example, 
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Console.WriteLine("The current culture is \"{0}\" - {1}.", 
                       Thread.CurrentThread.CurrentCulture.Name,
                       Thread.CurrentThread.CurrentCulture.DisplayName);

// Display the string to search for and the string to search.
    Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"", 
                       CapitalAWithRing, cat);
    Console.WriteLine();

// Note that in each of the following searches, we look for 
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
// the string was not found.
// Search using different values of StringComparsion. Specify the start 
// index and count. 

    Console.WriteLine("Part 1: Start index and count are specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }
    }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/

// This code example demonstrates the
// System.String.LastIndexOf(String, ..., StringComparison) methods.

open System
open System.Threading
open System.Globalization

let intro = "Find the last occurrence of a character using different values of StringComparison."

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
let CapitalAWithRing = "\u00c5"

// Define a string to search.
// The result of combining the characters LATIN SMALL LETTER A and COMBINING
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
let cat = "A Cheshire c" + "\u0061\u030a" + "t"
let loc = 0
let scValues = 
    [| StringComparison.CurrentCulture
       StringComparison.CurrentCultureIgnoreCase
       StringComparison.InvariantCulture
       StringComparison.InvariantCultureIgnoreCase
       StringComparison.Ordinal
       StringComparison.OrdinalIgnoreCase  |]

// Clear the screen and display an introduction.
Console.Clear()
printfn $"{intro}"

// Display the current culture because culture affects the result. For example,
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

Thread.CurrentThread.CurrentCulture <- CultureInfo "en-US"
printfn $"The current culture is \"{Thread.CurrentThread.CurrentCulture.Name}\" - {Thread.CurrentThread.CurrentCulture.DisplayName}."

// Display the string to search for and the string to search.
printfn $"Search for the string \"{CapitalAWithRing}\" in the string \"{cat}\"\n"

// Note that in each of the following searches, we look for
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates
// the string was not found.
// Search using different values of StringComparsion. Specify the start
// index and count.

printfn "Part 1: Start index and count are specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

// Search using different values of StringComparsion. Specify the
// start index.
printfn "\nPart 2: Start index is specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

// Search using different values of StringComparsion.
printfn "\nPart 3: Neither start index nor count is specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

(*
Note: This code example was executed on a console whose user interface
culture is "en-US" (English-United States).

This code example produces the following results:

Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*)

' This code example demonstrates the 
' System.String.LastIndexOf(String, ..., StringComparison) methods.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the last occurrence of a character using different " & _
                              "values of StringComparison."
        Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
        
        ' Define a string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim CapitalAWithRing As String = "Å"
        
        ' Define a string to search. 
        ' The result of combining the characters LATIN SMALL LETTER A and COMBINING 
        ' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
        ' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
        Dim cat As String = "A Cheshire c" & "å" & "t"
        Dim loc As Integer = 0
        Dim scValues As StringComparison() =  { _
                        StringComparison.CurrentCulture, _
                        StringComparison.CurrentCultureIgnoreCase, _
                        StringComparison.InvariantCulture, _
                        StringComparison.InvariantCultureIgnoreCase, _
                        StringComparison.Ordinal, _
                        StringComparison.OrdinalIgnoreCase }
        Dim sc As StringComparison
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        Console.WriteLine(intro)
        
        ' Display the current culture because culture affects the result. For example, 
        ' try this code example with the "sv-SE" (Swedish-Sweden) culture.
        Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
        Console.WriteLine("The current culture is ""{0}"" - {1}.", _
                           Thread.CurrentThread.CurrentCulture.Name, _
                           Thread.CurrentThread.CurrentCulture.DisplayName)
        
        ' Display the string to search for and the string to search.
        Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
                           CapitalAWithRing, cat)
        Console.WriteLine()
        
        ' Note that in each of the following searches, we look for 
        ' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
        ' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
        ' the string was not found.
        ' Search using different values of StringComparsion. Specify the start 
        ' index and count. 
        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. Specify the 
        ' start index. 
        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. 
        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub
End Class

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the last occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Поиск начинается с позиции startIndex символов и продолжается назад, пока не будет найдена value или count позиции символов были проверены. Например, если startIndexLength – 1, метод выполняет поиск назад count символов из последнего символа строки.

Параметр comparisonType указывает, чтобы найти параметр value с помощью:

• Текущий или инвариантный язык и региональные параметры.
• Поиск без учета регистра или регистра.
• Правила сравнения слов или порядкового номера.

Примечания для тех, кто вызывает этот метод

Наборы символов включают игнорируемые символы, которые не учитываются при выполнении лингвистического или языка и региональных параметров. В поиске с учетом языка и региональных параметров (то есть если comparisonType не Ordinal или OrdinalIgnoreCase), если value содержит игнорируемый символ, результат эквивалентен поиску с помощью этого символа.

В следующем примере метод LastIndexOf(String, Int32, Int32, StringComparison) используется для поиска позиции мягкого дефиса (U+00AD), за которым следует "m" во всех, кроме первой позиции символа до окончательного "m" в двух строках. Только одна из строк содержит необходимую подстроку. Если пример выполняется в .NET Framework 4 или более поздней версии, в обоих случаях, так как мягкий дефис является игнорируемым символом, метод возвращает индекс "m" в строке при выполнении сравнения с учетом языка и региональных параметров. Однако при выполнении порядкового сравнения она находит подстроку только в первой строке. Обратите внимание, что в случае первой строки, которая включает мягкий дефис, за которым следует "m", метод возвращает индекс "m" при выполнении сравнения с учетом языка и региональных параметров. Метод возвращает индекс мягкого дефиса в первой строке только при выполнении порядкового сравнения.

string searchString = "\u00ADm";

string s1 = "ani\u00ADmal";
string s2 = "animal";

int position;

position = s1.LastIndexOf('m');
if (position >= 1)
{
    Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture));
    Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.Ordinal));
}

position = s2.LastIndexOf('m');
if (position >= 1)
{
    Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture));
    Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.Ordinal));
}

// The example displays the following output:
//
// 4
// 3
// 3
// -1

let searchString = "\u00ADm"

let s1 = "ani\u00ADmal"
let s2 = "animal"

let position = s1.LastIndexOf 'm'
if position >= 1 then
    printfn $"{s1.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture)}"
    printfn $"{s1.LastIndexOf(searchString, position, position, StringComparison.Ordinal)}"

let position = s2.LastIndexOf 'm'
if position >= 1 then
    printfn $"{s2.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture)}"
    printfn $"{s2.LastIndexOf(searchString, position, position, StringComparison.Ordinal)}"

// The example displays the following output:
//
// 4
// 3
// 3
// -1

Dim searchString As String = ChrW(&HAD) + "m"

Dim s1 As String = "ani" + ChrW(&HAD) + "m"
Dim s2 As String = "animal"

Dim position As Integer

position = s1.LastIndexOf("m"c)
If position >= 1 Then
    Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture))
    Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.Ordinal))
End If

position = s2.LastIndexOf("m"c)
If position >= 1 Then
    Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture))
    Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.Ordinal))
End If

' The example displays the following output:
'
' 4
' 3
' 3
' -1

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(System::String ^ value, int startIndex, int count);

public int LastIndexOf (string value, int startIndex, int count);

member this.LastIndexOf : string * int * int -> int

Public Function LastIndexOf (value As String, startIndex As Integer, count As Integer) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение начального индекса value, если эта строка найдена или -1, если она не найдена или если текущий экземпляр равен Empty.

Исключения

Примеры

В следующем примере индекс всех вхождения строки в подстроке, работающей с конца подстроки до начала подстроки.

// Sample for String::LastIndexOf(String, Int32, Int32)
using namespace System;
int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
   String^ br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
   String^ str = "Now is the time for all good men to come to the aid of their party.";
   int start;
   int at;
   int count;
   int end;
   start = str->Length - 1;
   end = start / 2 - 1;
   Console::WriteLine( "All occurrences of 'he' from position {0} to {1}.", start, end );
   Console::WriteLine( "{1}{0}{2}{0}{3}{0}", Environment::NewLine, br1, br2, str );
   Console::Write( "The string 'he' occurs at position(s): " );
   count = 0;
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      count = start - end; //Count must be within the substring.
      at = str->LastIndexOf( "he", start, count );
      if ( at > -1 )
      {
         Console::Write( "{0} ", at );
         start = at - 1;
      }
   }

   Console::Write( "{0} {0} {0}", Environment::NewLine );
}

/*
This example produces the following results:
All occurrences of 'he' from position 66 to 32.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 56 45
*/

// Sample for String.LastIndexOf(String, Int32, Int32)
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;
    int count;
    int end;

    start = str.Length-1;
    end = start/2 - 1;
    Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, end);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The string 'he' occurs at position(s): ");

    count = 0;
    at = 0;
    while((start > -1) && (at > -1))
        {
        count = start - end; //Count must be within the substring.
        at = str.LastIndexOf("he", start, count);
        if (at > -1)
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 'he' from position 66 to 32.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 56 45
*/

// Sample for String.LastIndexOf(String, Int32, Int32)
open System

let br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
let br2 = "0123456789012345678901234567890123456789012345678901234567890123456"
let str = "Now is the time for all good men to come to the aid of their party."

let mutable start = str.Length-1
let last = start / 2 - 1
printfn $"All occurrences of 'he' from position {start} to {last}."
printfn $"{br1}{Environment.NewLine}{br2}{Environment.NewLine}{str}{Environment.NewLine}"
printf "The string 'he' occurs at position(s): "

let mutable at = 0
while (start > -1) && (at > -1) do
    let count = start - last //Count must be within the substring.
    at <- str.LastIndexOf("he", start, count)
    if at > -1 then
        printf $"{at} "
        start <- at - 1
printf $"{Environment.NewLine}{Environment.NewLine}{Environment.NewLine}"
(*
This example produces the following results:
All occurrences of 'he' from position 66 to 32.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 56 45
*)

' Sample for String.LastIndexOf(String, Int32, Int32)
 _

Class Sample
   
   Public Shared Sub Main()
      
      Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
      Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
      Dim str As String = "Now is the time for all good men to come to the aid of their party."
      Dim start As Integer
      Dim at As Integer
      Dim count As Integer
      Dim [end] As Integer

      start = str.Length - 1
      [end] = start / 2 - 1
      Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, [end])
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The string 'he' occurs at position(s): ")
      
      count = 0
      at = 0
      While start > - 1 And at > - 1
         count = start - [end] 'Count must be within the substring.
         at = str.LastIndexOf("he", start, count)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 'he' from position 66 to 32.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The string 'he' occurs at position(s): 56 45
'
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Поиск начинается с startIndex позиции символов этого экземпляра и переходит к началу, пока не будет найдена value или count позиции символов были проверены. Например, если startIndexLength – 1, метод выполняет поиск назад count символов из последнего символа строки.

Этот метод выполняет поиск слова (с учетом регистра и языка и региональных параметров) с помощью текущего языка и региональных параметров.

Наборы символов включают игнорируемые символы, которые не учитываются при выполнении лингвистического или языка и региональных параметров. В поиске с учетом языка и региональных параметров, если value содержит игнорируемый символ, результат эквивалентен поиску с помощью этого символа.

В следующем примере метод LastIndexOf используется для поиска позиции мягкого дефиса (U+00AD), за которым следует "m" или "n" в двух строках. Только одна из строк содержит мягкий дефис. В случае строки, которая включает мягкий дефис, за которым следует "m", LastIndexOf возвращает индекс "m" при поиске мягкого дефиса, за которым следует "m".

int position = 0;
string s1 = "ani\u00ADmal";
string s2 = "animal";

// Find the index of the soft hyphen followed by "n".
position = s1.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s1.LastIndexOf("\u00ADn", position, position + 1));

position = s2.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s2.LastIndexOf("\u00ADn", position, position + 1));

// Find the index of the soft hyphen followed by "m".
position = s1.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s1.LastIndexOf("\u00ADm", position, position + 1));

position = s2.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s2.LastIndexOf("\u00ADm", position, position + 1));

// The example displays the following output:
//
// 'm' at position 4
// 1
// 'm' at position 3
// 1
// 'm' at position 4
// 4
// 'm' at position 3
// 3

let s1 = "ani\u00ADmal"
let s2 = "animal"

// Find the index of the soft hyphen followed by "n".
let position = s1.LastIndexOf "m"
printfn $"'m' at position {position}"

if position  >= 0 then
    printfn $"""{s1.LastIndexOf("\u00ADn", position, position + 1)}"""

let position = s2.LastIndexOf "m"
printfn $"'m' at position {position}"

if position  >= 0 then
    printfn $"""{s2.LastIndexOf("\u00ADn", position, position + 1)}"""

// Find the index of the soft hyphen followed by "m".
let position = s1.LastIndexOf "m"
printfn $"'m' at position {position}"

if position  >= 0 then
    printfn $"""{s1.LastIndexOf("\u00ADm", position, position + 1)}"""

let position = s2.LastIndexOf "m"
printfn $"'m' at position {position}"

if position  >= 0 then
    printfn $"""{s2.LastIndexOf("\u00ADm", position, position + 1)}"""

// The example displays the following output:
//
// 'm' at position 4
// 1
// 'm' at position 3
// 1
// 'm' at position 4
// 4
// 'm' at position 3
// 3

Dim position As Integer
Dim softHyphen As String = ChrW(&HAD)

Dim s1 As String = "ani" + softHyphen + "mal"
Dim s2 As String = "animal"

' Find the index of the soft hyphen followed by "n".
position = s1.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s1.LastIndexOf(softHyphen + "n", position, position + 1))
End If

position = s2.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s2.LastIndexOf(softHyphen + "n", position, position + 1))
End If

' Find the index of the soft hyphen followed by "m".
position = s1.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s1.LastIndexOf(softHyphen + "m", position, position + 1))
End If

position = s2.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s2.LastIndexOf(softHyphen + "m", position, position + 1))
End If

' The example displays the following output:
'
' 'm' at position 4
' 1
' 'm' at position 3
' 1
' 'm' at position 4
' 4
' 'm' at position 3
' 3

Примечания для тех, кто вызывает этот метод

Как описано в рекомендации по использованию строк, рекомендуется избегать вызова методов сравнения строк, заменяющих значения по умолчанию и вызывающих методы, требующие явного указания параметров. Чтобы выполнить эту операцию с помощью правил сравнения текущего языка и региональных параметров, явно сообщите о намерении путем вызова перегрузки метода LastIndexOf(String, Int32, Int32, StringComparison) значением CurrentCulture для параметра comparisonType. Если вам не требуется лингвистическое сравнение, рассмотрите возможность использования Ordinal.

См. также раздел

• Int32
• IndexOf(Char)
• IndexOfAny(Char[])
• LastIndexOfAny(Char[])

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(char value, int startIndex, int count);

public int LastIndexOf (char value, int startIndex, int count);

member this.LastIndexOf : char * int * int -> int

Public Function LastIndexOf (value As Char, startIndex As Integer, count As Integer) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение индекса value, если этот символ найден или -1, если он не найден или если текущий экземпляр равен Empty.

Исключения

Примеры

Следующий пример находит индекс всех вхождения символов в подстроке, работая с конца подстроки до начала подстроки.

// Sample for String::LastIndexOf(Char, Int32, Int32)
using namespace System;
int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
   String^ br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
   String^ str = "Now is the time for all good men to come to the aid of their party.";
   int start;
   int at;
   int count;
   int end;
   start = str->Length - 1;
   end = start / 2 - 1;
   Console::WriteLine( "All occurrences of 't' from position {0} to {1}.", start, end );
   Console::WriteLine( "\n{0}\n{1}\n{2}", br1, br2, str );
   Console::Write( "The letter 't' occurs at position(s): " );
   count = 0;
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      count = start - end; //Count must be within the substring.
      at = str->LastIndexOf( 't', start, count );
      if ( at > -1 )
      {
         Console::Write( " {0} ", at );
         start = at - 1;
      }
   }
}

/*
This example produces the following results:
All occurrences of 't' from position 66 to 32.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33


*/

// Sample for String.LastIndexOf(Char, Int32, Int32)
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;
    int count;
    int end;

    start = str.Length-1;
    end = start/2 - 1;
    Console.WriteLine("All occurrences of 't' from position {0} to {1}.", start, end);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The letter 't' occurs at position(s): ");

    count = 0;
    at = 0;
    while((start > -1) && (at > -1))
        {
        count = start - end; //Count must be within the substring.
        at = str.LastIndexOf('t', start, count);
        if (at > -1)
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 't' from position 66 to 32.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33


*/

// Sample for String.LastIndexOf(Char, Int32, Int32)
open System

let br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
let br2 = "0123456789012345678901234567890123456789012345678901234567890123456"
let str = "Now is the time for all good men to come to the aid of their party."

let mutable start = str.Length-1
let last = start / 2 - 1
printfn $"All occurrences of 't' from position {start} to {last}."
printfn $"{br1}{Environment.NewLine}{br2}{Environment.NewLine}{str}{Environment.NewLine}"
printf "The letter 't' occurs at position(s): "

let mutable at = 0
while (start > -1) && (at > -1) do
    let count = start - last //Count must be within the substring.
    at <- str.LastIndexOf('t', start, count)
    if at > -1 then
        printf $"{at} "
        start <- at - 1
printf $"{Environment.NewLine}{Environment.NewLine}{Environment.NewLine}"
(*
This example produces the following results:
All occurrences of 't' from position 66 to 32.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33


*)

' Sample for String.LastIndexOf(Char, Int32, Int32)
 _

Class Sample
   
   Public Shared Sub Main()
      
      Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
      Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
      Dim str As String = "Now is the time for all good men to come to the aid of their party."
      Dim start As Integer
      Dim at As Integer
      Dim count As Integer
      Dim [end] As Integer

      start = str.Length - 1
      [end] = start / 2 - 1
      Console.WriteLine("All occurrences of 't' from position {0} to {1}.", start, [end])
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The letter 't' occurs at position(s): ")
      
      count = 0
      at = 0
      While start > - 1 And at > - 1
         count = start - [end] 'Count must be within the substring.
         at = str.LastIndexOf("t"c, start, count)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 't' from position 66 to 32.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The letter 't' occurs at position(s): 64 55 44 41 33
'
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Этот метод начинает поиск по startIndex позиции символов и переходит к началу этого экземпляра до тех пор, пока не будет найдена value или count позиции символов были проверены. Например, если startIndexLength – 1, метод выполняет поиск назад count символов из последнего символа строки. Поиск учитывает регистр.

Этот метод выполняет порядковый поиск (без учета языка и региональных параметров), где символ считается эквивалентным другому символу, только если их скалярное значение Юникода совпадает. Чтобы выполнить поиск с учетом языка и региональных параметров, используйте метод CompareInfo.LastIndexOf, где скалярное значение Юникода, представляющее предварительно скомпилированные символы, например ligature "Æ" (U+00C6), может считаться эквивалентным любому вхождлению компонентов символа в правильной последовательности, например "AE" (U+0041, U+0045) в зависимости от языка и региональных параметров.

См. также раздел

• Char
• Int32
• IndexOf(Char)
• IndexOfAny(Char[])
• LastIndexOfAny(Char[])

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(System::String ^ value, StringComparison comparisonType);

public int LastIndexOf (string value, StringComparison comparisonType);

member this.LastIndexOf : string * StringComparison -> int

Public Function LastIndexOf (value As String, comparisonType As StringComparison) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение начального индекса параметра value, если эта строка найдена, или -1, если это не так.

Исключения

Примеры

В следующем примере показаны три перегрузки метода LastIndexOf, которые находят последнее вхождение строки в другой строке с использованием различных значений перечисления StringComparison.

// This code example demonstrates the 
// System.String.LastIndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the last occurrence of a character using different " + 
                   "values of StringComparison.";
    string resultFmt = "Comparison: {0,-28} Location: {1,3}";

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string CapitalAWithRing = "\u00c5"; 

// Define a string to search. 
// The result of combining the characters LATIN SMALL LETTER A and COMBINING 
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
    string cat = "A Cheshire c" + "\u0061\u030a" + "t";
    int loc = 0;
    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

// Clear the screen and display an introduction.
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because culture affects the result. For example, 
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Console.WriteLine("The current culture is \"{0}\" - {1}.", 
                       Thread.CurrentThread.CurrentCulture.Name,
                       Thread.CurrentThread.CurrentCulture.DisplayName);

// Display the string to search for and the string to search.
    Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"", 
                       CapitalAWithRing, cat);
    Console.WriteLine();

// Note that in each of the following searches, we look for 
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
// the string was not found.
// Search using different values of StringComparsion. Specify the start 
// index and count. 

    Console.WriteLine("Part 1: Start index and count are specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }
    }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/

// This code example demonstrates the
// System.String.LastIndexOf(String, ..., StringComparison) methods.

open System
open System.Threading
open System.Globalization

let intro = "Find the last occurrence of a character using different values of StringComparison."

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
let CapitalAWithRing = "\u00c5"

// Define a string to search.
// The result of combining the characters LATIN SMALL LETTER A and COMBINING
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
let cat = "A Cheshire c" + "\u0061\u030a" + "t"
let loc = 0
let scValues = 
    [| StringComparison.CurrentCulture
       StringComparison.CurrentCultureIgnoreCase
       StringComparison.InvariantCulture
       StringComparison.InvariantCultureIgnoreCase
       StringComparison.Ordinal
       StringComparison.OrdinalIgnoreCase  |]

// Clear the screen and display an introduction.
Console.Clear()
printfn $"{intro}"

// Display the current culture because culture affects the result. For example,
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

Thread.CurrentThread.CurrentCulture <- CultureInfo "en-US"
printfn $"The current culture is \"{Thread.CurrentThread.CurrentCulture.Name}\" - {Thread.CurrentThread.CurrentCulture.DisplayName}."

// Display the string to search for and the string to search.
printfn $"Search for the string \"{CapitalAWithRing}\" in the string \"{cat}\"\n"

// Note that in each of the following searches, we look for
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates
// the string was not found.
// Search using different values of StringComparsion. Specify the start
// index and count.

printfn "Part 1: Start index and count are specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

// Search using different values of StringComparsion. Specify the
// start index.
printfn "\nPart 2: Start index is specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

// Search using different values of StringComparsion.
printfn "\nPart 3: Neither start index nor count is specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

(*
Note: This code example was executed on a console whose user interface
culture is "en-US" (English-United States).

This code example produces the following results:

Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*)

' This code example demonstrates the 
' System.String.LastIndexOf(String, ..., StringComparison) methods.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the last occurrence of a character using different " & _
                              "values of StringComparison."
        Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
        
        ' Define a string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim CapitalAWithRing As String = "Å"
        
        ' Define a string to search. 
        ' The result of combining the characters LATIN SMALL LETTER A and COMBINING 
        ' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
        ' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
        Dim cat As String = "A Cheshire c" & "å" & "t"
        Dim loc As Integer = 0
        Dim scValues As StringComparison() =  { _
                        StringComparison.CurrentCulture, _
                        StringComparison.CurrentCultureIgnoreCase, _
                        StringComparison.InvariantCulture, _
                        StringComparison.InvariantCultureIgnoreCase, _
                        StringComparison.Ordinal, _
                        StringComparison.OrdinalIgnoreCase }
        Dim sc As StringComparison
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        Console.WriteLine(intro)
        
        ' Display the current culture because culture affects the result. For example, 
        ' try this code example with the "sv-SE" (Swedish-Sweden) culture.
        Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
        Console.WriteLine("The current culture is ""{0}"" - {1}.", _
                           Thread.CurrentThread.CurrentCulture.Name, _
                           Thread.CurrentThread.CurrentCulture.DisplayName)
        
        ' Display the string to search for and the string to search.
        Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
                           CapitalAWithRing, cat)
        Console.WriteLine()
        
        ' Note that in each of the following searches, we look for 
        ' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
        ' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
        ' the string was not found.
        ' Search using different values of StringComparsion. Specify the start 
        ' index and count. 
        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. Specify the 
        ' start index. 
        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. 
        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub
End Class

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the last occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Параметр comparisonType указывает, чтобы найти параметр value с помощью:

• Текущий или инвариантный язык и региональные параметры.
• Поиск без учета регистра или регистра.
• Правила сравнения слов или порядкового номера.

Поиск начинается с последней позиции символа этого экземпляра и продолжается назад к началу до тех пор, пока не будет найдена value или будет проверена первая позиция символа.

Примечания для тех, кто вызывает этот метод

Наборы символов включают игнорируемые символы, которые не учитываются при выполнении лингвистического или языка и региональных параметров. В поиске с учетом языка и региональных параметров (то есть если options не Ordinal или OrdinalIgnoreCase), если value содержит игнорируемый символ, результат эквивалентен поиску с помощью этого символа.

В следующем примере метод LastIndexOf(String, StringComparison) используется для поиска двух подстроок (обратимого дефиса, за которым следует "n" и обратимого дефиса, а затем "m") в двух строках. Только одна из строк содержит мягкий дефис. Если пример выполняется в .NET Framework 4 или более поздней версии, так как обратимый дефис является игнорируемым символом, поиск с учетом языка и региональных параметров возвращает то же значение, что он возвращает, если обратимый дефис не был включен в строку поиска. Однако порядковый поиск успешно находит мягкий дефис в одной строке и сообщает, что он отсутствует во второй строке.

string s1 = "ani\u00ADmal";
string s2 = "animal";

Console.WriteLine("Culture-sensitive comparison:");

// Use culture-sensitive comparison to find the last soft hyphen followed by "n".
Console.WriteLine(s1.LastIndexOf("\u00ADn", StringComparison.CurrentCulture));
Console.WriteLine(s2.LastIndexOf("\u00ADn", StringComparison.CurrentCulture));

// Use culture-sensitive comparison to find the last soft hyphen followed by "m".
Console.WriteLine(s1.LastIndexOf("\u00ADm", StringComparison.CurrentCulture));
Console.WriteLine(s2.LastIndexOf("\u00ADm", StringComparison.CurrentCulture));

Console.WriteLine("Ordinal comparison:");

// Use ordinal comparison to find the last soft hyphen followed by "n".
Console.WriteLine(s1.LastIndexOf("\u00ADn", StringComparison.Ordinal));
Console.WriteLine(s2.LastIndexOf("\u00ADn", StringComparison.Ordinal));

// Use ordinal comparison to find the last soft hyphen followed by "m".
Console.WriteLine(s1.LastIndexOf("\u00ADm", StringComparison.Ordinal));
Console.WriteLine(s2.LastIndexOf("\u00ADm", StringComparison.Ordinal));

// The example displays the following output:
//
// Culture-sensitive comparison:
// 1
// 1
// 4
// 3
// Ordinal comparison:
// -1
// -1
// 3
// -1

open System

let s1 = "ani\u00ADmal"
let s2 = "animal"

printfn "Culture-sensitive comparison:"

// Use culture-sensitive comparison to find the last soft hyphen followed by "n".
printfn $"""{s1.LastIndexOf("\u00ADn", StringComparison.CurrentCulture)}"""
printfn $"""{s2.LastIndexOf("\u00ADn", StringComparison.CurrentCulture)}"""

// Use culture-sensitive comparison to find the last soft hyphen followed by "m".
printfn $"""{s1.LastIndexOf("\u00ADm", StringComparison.CurrentCulture)}"""
printfn $"""{s2.LastIndexOf("\u00ADm", StringComparison.CurrentCulture)}"""

printfn "Ordinal comparison:"

// Use ordinal comparison to find the last soft hyphen followed by "n".
printfn $"""{s1.LastIndexOf("\u00ADn", StringComparison.Ordinal)}"""
printfn $"""{s2.LastIndexOf("\u00ADn", StringComparison.Ordinal)}"""

// Use ordinal comparison to find the last soft hyphen followed by "m".
printfn $"""{s1.LastIndexOf("\u00ADm", StringComparison.Ordinal)}"""
printfn $"""{s2.LastIndexOf("\u00ADm", StringComparison.Ordinal)}"""

// The example displays the following output:
//
// Culture-sensitive comparison:
// 1
// 1
// 4
// 3
// Ordinal comparison:
// -1
// -1
// 3
// -1

Dim softHyphen As String = ChrW(&HAD)
Dim s1 As String = "ani" + softHyphen + "mal"
Dim s2 As String = "animal"

Console.WriteLine("Culture-sensitive comparison:")

' Use culture-sensitive comparison to find the last soft hyphen followed by "n".
Console.WriteLine(s1.LastIndexOf(softHyphen + "n", StringComparison.CurrentCulture))
Console.WriteLine(s2.LastIndexOf(softHyphen + "n", StringComparison.CurrentCulture))

' Use culture-sensitive comparison to find the last soft hyphen followed by "m".
Console.WriteLine(s1.LastIndexOf(softHyphen + "m", StringComparison.CurrentCulture))
Console.WriteLine(s2.LastIndexOf(softHyphen + "m", StringComparison.CurrentCulture))

Console.WriteLine("Ordinal comparison:")

' Use ordinal comparison to find the last soft hyphen followed by "n".
Console.WriteLine(s1.LastIndexOf(softHyphen + "n", StringComparison.Ordinal))
Console.WriteLine(s2.LastIndexOf(softHyphen + "n", StringComparison.Ordinal))

' Use ordinal comparison to find the last soft hyphen followed by "m".
Console.WriteLine(s1.LastIndexOf(softHyphen + "m", StringComparison.Ordinal))
Console.WriteLine(s2.LastIndexOf(softHyphen + "m", StringComparison.Ordinal))

' The example displays the following output:
'
' Culture-sensitive comparison:
' 1
' 1
' 4
' 3
' Ordinal comparison:
' -1
' -1
' 3
' -1

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(System::String ^ value, int startIndex, StringComparison comparisonType);

public int LastIndexOf (string value, int startIndex, StringComparison comparisonType);

member this.LastIndexOf : string * int * StringComparison -> int

Public Function LastIndexOf (value As String, startIndex As Integer, comparisonType As StringComparison) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение начального индекса параметра value, если эта строка найдена, или -1, если она не найдена или если текущий экземпляр равен Empty.

Исключения

Примеры

В следующем примере показаны три перегрузки метода LastIndexOf, которые находят последнее вхождение строки в другой строке с использованием различных значений перечисления StringComparison.

// This code example demonstrates the 
// System.String.LastIndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the last occurrence of a character using different " + 
                   "values of StringComparison.";
    string resultFmt = "Comparison: {0,-28} Location: {1,3}";

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string CapitalAWithRing = "\u00c5"; 

// Define a string to search. 
// The result of combining the characters LATIN SMALL LETTER A and COMBINING 
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
    string cat = "A Cheshire c" + "\u0061\u030a" + "t";
    int loc = 0;
    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

// Clear the screen and display an introduction.
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because culture affects the result. For example, 
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Console.WriteLine("The current culture is \"{0}\" - {1}.", 
                       Thread.CurrentThread.CurrentCulture.Name,
                       Thread.CurrentThread.CurrentCulture.DisplayName);

// Display the string to search for and the string to search.
    Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"", 
                       CapitalAWithRing, cat);
    Console.WriteLine();

// Note that in each of the following searches, we look for 
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
// the string was not found.
// Search using different values of StringComparsion. Specify the start 
// index and count. 

    Console.WriteLine("Part 1: Start index and count are specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }
    }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/

// This code example demonstrates the
// System.String.LastIndexOf(String, ..., StringComparison) methods.

open System
open System.Threading
open System.Globalization

let intro = "Find the last occurrence of a character using different values of StringComparison."

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
let CapitalAWithRing = "\u00c5"

// Define a string to search.
// The result of combining the characters LATIN SMALL LETTER A and COMBINING
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
let cat = "A Cheshire c" + "\u0061\u030a" + "t"
let loc = 0
let scValues = 
    [| StringComparison.CurrentCulture
       StringComparison.CurrentCultureIgnoreCase
       StringComparison.InvariantCulture
       StringComparison.InvariantCultureIgnoreCase
       StringComparison.Ordinal
       StringComparison.OrdinalIgnoreCase  |]

// Clear the screen and display an introduction.
Console.Clear()
printfn $"{intro}"

// Display the current culture because culture affects the result. For example,
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

Thread.CurrentThread.CurrentCulture <- CultureInfo "en-US"
printfn $"The current culture is \"{Thread.CurrentThread.CurrentCulture.Name}\" - {Thread.CurrentThread.CurrentCulture.DisplayName}."

// Display the string to search for and the string to search.
printfn $"Search for the string \"{CapitalAWithRing}\" in the string \"{cat}\"\n"

// Note that in each of the following searches, we look for
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates
// the string was not found.
// Search using different values of StringComparsion. Specify the start
// index and count.

printfn "Part 1: Start index and count are specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

// Search using different values of StringComparsion. Specify the
// start index.
printfn "\nPart 2: Start index is specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

// Search using different values of StringComparsion.
printfn "\nPart 3: Neither start index nor count is specified."
for sc in scValues do
    let loc = cat.LastIndexOf(CapitalAWithRing, sc)
    printfn $"Comparison: {sc,-28} Location: {loc,3}"

(*
Note: This code example was executed on a console whose user interface
culture is "en-US" (English-United States).

This code example produces the following results:

Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*)

' This code example demonstrates the 
' System.String.LastIndexOf(String, ..., StringComparison) methods.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the last occurrence of a character using different " & _
                              "values of StringComparison."
        Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
        
        ' Define a string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim CapitalAWithRing As String = "Å"
        
        ' Define a string to search. 
        ' The result of combining the characters LATIN SMALL LETTER A and COMBINING 
        ' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
        ' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
        Dim cat As String = "A Cheshire c" & "å" & "t"
        Dim loc As Integer = 0
        Dim scValues As StringComparison() =  { _
                        StringComparison.CurrentCulture, _
                        StringComparison.CurrentCultureIgnoreCase, _
                        StringComparison.InvariantCulture, _
                        StringComparison.InvariantCultureIgnoreCase, _
                        StringComparison.Ordinal, _
                        StringComparison.OrdinalIgnoreCase }
        Dim sc As StringComparison
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        Console.WriteLine(intro)
        
        ' Display the current culture because culture affects the result. For example, 
        ' try this code example with the "sv-SE" (Swedish-Sweden) culture.
        Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
        Console.WriteLine("The current culture is ""{0}"" - {1}.", _
                           Thread.CurrentThread.CurrentCulture.Name, _
                           Thread.CurrentThread.CurrentCulture.DisplayName)
        
        ' Display the string to search for and the string to search.
        Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
                           CapitalAWithRing, cat)
        Console.WriteLine()
        
        ' Note that in each of the following searches, we look for 
        ' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
        ' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
        ' the string was not found.
        ' Search using different values of StringComparsion. Specify the start 
        ' index and count. 
        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. Specify the 
        ' start index. 
        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. 
        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub
End Class

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the last occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Поиск начинается с позиции startIndex символа и продолжается назад до тех пор, пока не будет найдена value или будет рассмотрена первая позиция символа. Например, если startIndexLength – 1, метод выполняет поиск каждого символа из последнего символа в строке до начала.

Параметр comparisonType указывает, чтобы искать параметр value с использованием текущего или инвариантного языка и региональных параметров с учетом регистра или без учета регистра, а также использовать правила сравнения слов или порядковых значений.

Примечания для тех, кто вызывает этот метод

Наборы символов включают игнорируемые символы, которые не учитываются при выполнении лингвистического или языка и региональных параметров. В поиске с учетом языка и региональных параметров (то есть если comparisonType не Ordinal или OrdinalIgnoreCase), если value содержит игнорируемый символ, результат эквивалентен поиску с помощью этого символа.

В следующем примере метод LastIndexOf(String, Int32, StringComparison) используется для поиска позиции мягкого дефиса (U+00AD), за которым следует "m", начиная с окончательного "m" в двух строках. Только одна из строк содержит необходимую подстроку. Если пример выполняется в .NET Framework 4 или более поздней версии, в обоих случаях, так как мягкий дефис является игнорируемым символом, метод возвращает индекс "m" в строке при выполнении сравнения с учетом языка и региональных параметров. Обратите внимание, что в случае первой строки, которая включает мягкий дефис, за которым следует "m", метод возвращает индекс "m", а не индекс мягкого дефиса. Метод возвращает индекс мягкого дефиса в первой строке только при выполнении порядкового сравнения.

string searchString = "\u00ADm";

string s1 = "ani\u00ADmal";
string s2 = "animal";

int position;

position = s1.LastIndexOf('m');
if (position >= 0)
{
    Console.WriteLine(s1.LastIndexOf(searchString, position, StringComparison.CurrentCulture));
    Console.WriteLine(s1.LastIndexOf(searchString, position, StringComparison.Ordinal));
}

position = s2.LastIndexOf('m');
if (position >= 0)
{
    Console.WriteLine(s2.LastIndexOf(searchString, position, StringComparison.CurrentCulture));
    Console.WriteLine(s2.LastIndexOf(searchString, position, StringComparison.Ordinal));
}

// The example displays the following output:
//
// 4
// 3
// 3
// -1

    let searchString = "\u00ADm"

    let s1 = "ani\u00ADmal"
    let s2 = "animal"

    let position = s1.LastIndexOf 'm'
    if position >= 0 then
        printfn $"{s1.LastIndexOf(searchString, position, StringComparison.CurrentCulture)}"
        printfn $"{s1.LastIndexOf(searchString, position, StringComparison.Ordinal)}"

    let position = s2.LastIndexOf 'm'
    if position >= 0 then
        printfn $"{s2.LastIndexOf(searchString, position, StringComparison.CurrentCulture)}"
        printfn $"{s2.LastIndexOf(searchString, position, StringComparison.Ordinal)}"

// The example displays the following output:
//
// 4
// 3
// 3
// -1

Dim searchString As String = ChrW(&HAD) + "m"

Dim s1 As String = "ani" + ChrW(&HAD) + "mal"
Dim s2 As String = "animal"

Dim position As Integer

position = s1.LastIndexOf("m"c)
If position >= 0 Then
    Console.WriteLine(s1.LastIndexOf(searchString, position, StringComparison.CurrentCulture))
    Console.WriteLine(s1.LastIndexOf(searchString, position, StringComparison.Ordinal))
End If

position = s2.LastIndexOf("m"c)
If position >= 0 Then
    Console.WriteLine(s2.LastIndexOf(searchString, position, StringComparison.CurrentCulture))
    Console.WriteLine(s2.LastIndexOf(searchString, position, StringComparison.Ordinal))
End If

' The example displays the following output:
'
' 4
' 3
' 3
' -1

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(char value, int startIndex);

public int LastIndexOf (char value, int startIndex);

member this.LastIndexOf : char * int -> int

Public Function LastIndexOf (value As Char, startIndex As Integer) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение индекса value, если этот символ найден или -1, если он не найден или если текущий экземпляр равен Empty.

Исключения

Примеры

Следующий пример находит индекс всех вхождения символов в строке, работающих с конца строки до начала строки.

// Sample for String::LastIndexOf(Char, Int32)
using namespace System;
int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
   String^ br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
   String^ str = "Now is the time for all good men to come to the aid of their party.";
   int start;
   int at;
   start = str->Length - 1;
   Console::WriteLine( "All occurrences of 't' from position {0} to 0.", start );
   Console::WriteLine( "{0}\n{1}\n{2}\n", br1, br2, str );
   Console::Write( "The letter 't' occurs at position(s): " );
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      at = str->LastIndexOf( 't', start );
      if ( at > -1 )
      {
         Console::Write( " {0} ", at );
         start = at - 1;
      }
   }
}

/*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33 11 7
*/

// Sample for String.LastIndexOf(Char, Int32)
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;

    start = str.Length-1;
    Console.WriteLine("All occurrences of 't' from position {0} to 0.", start);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The letter 't' occurs at position(s): ");

    at = 0;
    while((start > -1) && (at > -1))
        {
        at = str.LastIndexOf('t', start);
        if (at > -1)
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33 11 7
*/

// Sample for String.LastIndexOf(Char, Int32)
open System

let br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
let br2 = "0123456789012345678901234567890123456789012345678901234567890123456"
let str = "Now is the time for all good men to come to the aid of their party."

let mutable start = str.Length - 1
printfn $"All occurrences of 't' from position {start} to 0."
printfn $"{br1}{Environment.NewLine}{br2}{Environment.NewLine}{str}{Environment.NewLine}"
printf "The letter 't' occurs at position(s): "

let mutable at = 0
while (start > -1) && (at > -1) do
    at <- str.LastIndexOf('t', start)
    if at > -1 then
        printf $"{at} "
        start <- at - 1
printf $"{Environment.NewLine}{Environment.NewLine}{Environment.NewLine}"
(*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33 11 7
*)

' Sample for String.LastIndexOf(Char, Int32)
Imports System 
 _

Class Sample
   
   Public Shared Sub Main()
      
      Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
      Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
      Dim str As String = "Now is the time for all good men to come to the aid of their party."
      Dim start As Integer
      Dim at As Integer
      
      start = str.Length - 1
      Console.WriteLine("All occurrences of 't' from position {0} to 0.", start)
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The letter 't' occurs at position(s): ")
      
      at = 0
      While start > - 1 And at > - 1
         at = str.LastIndexOf("t"c, start)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 't' from position 66 to 0.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The letter 't' occurs at position(s): 64 55 44 41 33 11 7
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1. Этот метод начинает поиск по startIndex позиции символа этого экземпляра и переходит к началу текущего экземпляра до тех пор, пока не будет найдена value или будет рассмотрена первая позиция символа. Например, если startIndexLength – 1, метод выполняет поиск каждого символа из последнего символа в строке до начала. Поиск учитывает регистр.

Этот метод выполняет порядковый поиск (без учета языка и региональных параметров), где символ считается эквивалентным другому символу, только если их скалярные значения Юникода совпадают. Чтобы выполнить поиск с учетом языка и региональных параметров, используйте метод CompareInfo.LastIndexOf, где скалярное значение Юникода, представляющее предварительно скомпилированные символы, например ligature "Æ" (U+00C6), может считаться эквивалентным любому вхождлению компонентов символа в правильной последовательности, например "AE" (U+0041, U+0045) в зависимости от языка и региональных параметров.

См. также раздел

• Char
• Int32
• IndexOf(Char)
• IndexOfAny(Char[])
• LastIndexOfAny(Char[])

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(System::String ^ value);

public int LastIndexOf (string value);

member this.LastIndexOf : string -> int

Public Function LastIndexOf (value As String) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение начального индекса value, если эта строка найдена или -1, если она отсутствует.

Исключения

Примеры

В следующем примере удаляются открывающие и закрывающие HTML-теги из строки, если теги начинаются и заканчиваются строкой. Если строка заканчивается символом закрывающей скобки (">"), в примере используется метод LastIndexOf для поиска начала конечного тега.

using System;

public class Example 
{
   public static void Main() 
   {
      string[] strSource = { "<b>This is bold text</b>", "<H1>This is large Text</H1>",
               "<b><i><font color=green>This has multiple tags</font></i></b>",
               "<b>This has <i>embedded</i> tags.</b>",
               "This line ends with a greater than symbol and should not be modified>" };

      // Strip HTML start and end tags from each string if they are present.
      foreach (string s in strSource)
      {
         Console.WriteLine("Before: " + s);
         string item = s;
         // Use EndsWith to find a tag at the end of the line.
         if (item.Trim().EndsWith(">")) 
         {
            // Locate the opening tag.
            int endTagStartPosition = item.LastIndexOf("</");
            // Remove the identified section, if it is valid.
            if (endTagStartPosition >= 0 )
               item = item.Substring(0, endTagStartPosition);

            // Use StartsWith to find the opening tag.
            if (item.Trim().StartsWith("<"))
            {
               // Locate the end of opening tab.
               int openTagEndPosition = item.IndexOf(">");
               // Remove the identified section, if it is valid.
               if (openTagEndPosition >= 0)
                  item = item.Substring(openTagEndPosition + 1);
            }      
         }
         // Display the trimmed string.
         Console.WriteLine("After: " + item);
         Console.WriteLine();
      }                   
   }
}
// The example displays the following output:
//    Before: <b>This is bold text</b>
//    After: This is bold text
//    
//    Before: <H1>This is large Text</H1>
//    After: This is large Text
//    
//    Before: <b><i><font color=green>This has multiple tags</font></i></b>
//    After: <i><font color=green>This has multiple tags</font></i>
//    
//    Before: <b>This has <i>embedded</i> tags.</b>
//    After: This has <i>embedded</i> tags.
//    
//    Before: This line ends with a greater than symbol and should not be modified>
//    After: This line ends with a greater than symbol and should not be modified>

let strSource = 
    [| "<b>This is bold text</b>"; "<H1>This is large Text</H1>"
       "<b><i><font color=green>This has multiple tags</font></i></b>"
       "<b>This has <i>embedded</i> tags.</b>"
       "This line ends with a greater than symbol and should not be modified>" |]

// Strip HTML start and end tags from each string if they are present.
for s in strSource do
    printfn $"Before: {s}"
    let mutable item = s
    // Use EndsWith to find a tag at the end of the line.
    if item.Trim().EndsWith ">" then
        // Locate the opening tag.
        let endTagStartPosition = item.LastIndexOf "</"
        // Remove the identified section, if it is valid.
        if endTagStartPosition >= 0 then
            item <- item.Substring(0, endTagStartPosition)

        // Use StartsWith to find the opening tag.
        if item.Trim().StartsWith "<" then
            // Locate the end of opening tab.
            let openTagEndPosition = item.IndexOf ">"
            // Remove the identified section, if it is valid.
            if openTagEndPosition >= 0 then
                item <- item.Substring(openTagEndPosition + 1)
    // Display the trimmed string.
    printfn "After: {item}"
    printfn ""
// The example displays the following output:
//    Before: <b>This is bold text</b>
//    After: This is bold text
//
//    Before: <H1>This is large Text</H1>
//    After: This is large Text
//
//    Before: <b><i><font color=green>This has multiple tags</font></i></b>
//    After: <i><font color=green>This has multiple tags</font></i>
//
//    Before: <b>This has <i>embedded</i> tags.</b>
//    After: This has <i>embedded</i> tags.
//
//    Before: This line ends with a greater than symbol and should not be modified>
//    After: This line ends with a greater than symbol and should not be modified>

Module Example
   Public Sub Main()
      Dim strSource As String() = { "<b>This is bold text</b>", _
                    "<H1>This is large Text</H1>", _
                    "<b><i><font color=green>This has multiple tags</font></i></b>", _
                    "<b>This has <i>embedded</i> tags.</b>", _
                    "This line ends with a greater than symbol and should not be modified>" }

      ' Strip HTML start and end tags from each string if they are present.
      For Each s As String In strSource
         Console.WriteLine("Before: " + s)
         ' Use EndsWith to find a tag at the end of the line.
         If s.Trim().EndsWith(">") Then 
            ' Locate the opening tag.
            Dim endTagStartPosition As Integer = s.LastIndexOf("</")
            ' Remove the identified section if it is valid.
            If endTagStartPosition >= 0 Then
               s = s.Substring(0, endTagStartPosition)
            End If
            
            ' Use StartsWith to find the opening tag.
            If s.Trim().StartsWith("<") Then
               ' Locate the end of opening tab.
               Dim openTagEndPosition As Integer = s.IndexOf(">")
               ' Remove the identified section if it is valid.
               If openTagEndPosition >= 0 Then
                  s = s.Substring(openTagEndPosition + 1)
               End If   
            End If      
         End If
         ' Display the trimmed string.
         Console.WriteLine("After: " + s)
         Console.WriteLine()
      Next                   
   End Sub
End Module
' The example displays the following output:
'    Before: <b>This is bold text</b>
'    After: This is bold text
'    
'    Before: <H1>This is large Text</H1>
'    After: This is large Text
'    
'    Before: <b><i><font color=green>This has multiple tags</font></i></b>
'    After: <i><font color=green>This has multiple tags</font></i>
'    
'    Before: <b>This has <i>embedded</i> tags.</b>
'    After: This has <i>embedded</i> tags.
'    
'    Before: This line ends with a greater than symbol and should not be modified>
'    After: This line ends with a greater than symbol and should not be modified>

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Поиск начинается с последней позиции символа этого экземпляра и продолжается назад к началу до тех пор, пока не будет найдена value или будет проверена первая позиция символа.

Этот метод выполняет поиск слова (с учетом регистра и языка и региональных параметров) с помощью текущего языка и региональных параметров.

Наборы символов включают игнорируемые символы, которые не учитываются при выполнении лингвистического или языка и региональных параметров. В поиске с учетом языка и региональных параметров, если value содержит игнорируемый символ, результат эквивалентен поиску с помощью этого символа.

В следующем примере метод LastIndexOf(String) используется для поиска двух подстроок (обратимого дефиса, за которым следует "n" и обратимого дефиса, а затем "m") в двух строках. Только одна из строк содержит мягкий дефис. Если пример выполняется в .NET Framework 4 или более поздней версии, в каждом случае, так как мягкий дефис является игнорируемым символом, результат будет таким же, как если бы мягкий дефис не был включен в value.

string s1 = "ani\u00ADmal";
string s2 = "animal";

// Find the index of the last soft hyphen followed by "n".
Console.WriteLine(s1.LastIndexOf("\u00ADn"));
Console.WriteLine(s2.LastIndexOf("\u00ADn"));

// Find the index of the last soft hyphen followed by "m".
Console.WriteLine(s1.LastIndexOf("\u00ADm"));
Console.WriteLine(s2.LastIndexOf("\u00ADm"));

// The example displays the following output:
//
// 1
// 1
// 4
// 3

let s1 = "ani\u00ADmal"
let s2 = "animal"

// Find the index of the last soft hyphen followed by "n".
printfn $"""{s1.LastIndexOf "\u00ADn"}"""
printfn $"""{s2.LastIndexOf "\u00ADn"}"""

// Find the index of the last soft hyphen followed by "m".
printfn $"""{s1.LastIndexOf "\u00ADm"}"""
printfn $"""{s2.LastIndexOf "\u00ADm"}"""

// The example displays the following output:
//
// 1
// 1
// 4
// 3

Dim softHyphen As String = ChrW(&HAD)
Dim s1 As String = "ani" + softHyphen + "mal"
Dim s2 As String = "animal"

' Find the index of the last soft hyphen followed by "n".
Console.WriteLine(s1.LastIndexOf(softHyphen + "n"))
Console.WriteLine(s2.LastIndexOf(softHyphen + "n"))

' Find the index of the last soft hyphen followed by "m".
Console.WriteLine(s1.LastIndexOf(softHyphen + "m"))
Console.WriteLine(s2.LastIndexOf(softHyphen + "m"))

' The example displays the following output:
'
' 1
' 1
' 4
' 3

Примечания для тех, кто вызывает этот метод

Как описано в рекомендации по использованию строк, рекомендуется избегать вызова методов сравнения строк, заменяющих значения по умолчанию и вызывающих методы, требующие явного указания параметров. Чтобы найти последний индекс подстроки в строковом экземпляре с помощью правил сравнения текущего языка и региональных параметров, явно сообщите о намерении путем вызова перегрузки метода LastIndexOf(String, StringComparison) значением CurrentCulture для параметра comparisonType. Если вам не требуется лингвистическое сравнение, рассмотрите возможность использования Ordinal.

См. также раздел

• Int32
• IndexOf(Char)
• IndexOfAny(Char[])
• LastIndexOfAny(Char[])

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(char value);

public int LastIndexOf (char value);

member this.LastIndexOf : char -> int

Public Function LastIndexOf (value As Char) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение индекса value, если этот символ найден или -1, если он отсутствует.

Примеры

В следующем примере определяется метод ExtractFilename, использующий метод LastIndexOf(Char) для поиска последнего символа разделителя каталогов в строке и извлечения имени файла строки. Если файл существует, метод возвращает имя файла без его пути.

using System;
using System.IO;

public class TestLastIndexOf
{
   public static void Main()
   {
      string filename;
      
      filename = ExtractFilename(@"C:\temp\");
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);
      
      filename = ExtractFilename(@"C:\temp\delegate.txt"); 
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);

      filename = ExtractFilename("delegate.txt");      
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);
      
      filename = ExtractFilename(@"C:\temp\notafile.txt");
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);
   }

   public static string ExtractFilename(string filepath)
   {
      // If path ends with a "\", it's a path only so return String.Empty.
      if (filepath.Trim().EndsWith(@"\"))
         return String.Empty;
      
      // Determine where last backslash is.
      int position = filepath.LastIndexOf('\\');
      // If there is no backslash, assume that this is a filename.
      if (position == -1)
      {
         // Determine whether file exists in the current directory.
         if (File.Exists(Environment.CurrentDirectory + Path.DirectorySeparatorChar + filepath)) 
            return filepath;
         else
            return String.Empty;
      }
      else
      {
         // Determine whether file exists using filepath.
         if (File.Exists(filepath))
            // Return filename without file path.
            return filepath.Substring(position + 1);
         else
            return String.Empty;
      }
   }
}

open System
open System.IO

let extractFilename (filepath: string) =
    // If path ends with a "\", it's a path only so return String.Empty.
    if filepath.Trim().EndsWith @"\" then
        String.Empty
    else
        // Determine where last backslash is.
        let position = filepath.LastIndexOf '\\'
        // If there is no backslash, assume that this is a filename.
        if position = -1 then
            // Determine whether file exists in the current directory.
            if File.Exists(Environment.CurrentDirectory + string Path.DirectorySeparatorChar + filepath) then
                filepath
            else
                String.Empty
        else
            // Determine whether file exists using filepath.
            if File.Exists filepath then
            // Return filename without file path.
                filepath.Substring(position + 1)
            else
                String.Empty

do
    let filename = extractFilename @"C:\temp\"
    printfn $"""{if String.IsNullOrEmpty filename then "<none>" else filename}"""

    let filename = extractFilename @"C:\temp\delegate.txt"
    printfn $"""{if String.IsNullOrEmpty filename then "<none>" else filename}"""

    let filename = extractFilename "delegate.txt"
    printfn $"""{if String.IsNullOrEmpty filename then "<none>" else filename}"""

    let filename = extractFilename @"C:\temp\notafile.txt"
    printfn $"""{if String.IsNullOrEmpty filename then "<none>" else filename}"""

Imports System.IO

Public Module Test
   Public Sub Main()
      Dim filename As String 
      
      filename = ExtractFilename("C:\temp\")
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))
      
      filename = ExtractFilename("C:\temp\delegate.txt") 
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))

      filename = ExtractFilename("delegate.txt")      
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))
      
      filename = ExtractFilename("C:\temp\notafile.txt")
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))
   End Sub
   
   Public Function ExtractFilename(filepath As String) As String
      ' If path ends with a "\", it's a path only so return String.Empty.
      If filepath.Trim().EndsWith("\") Then Return String.Empty
      
      ' Determine where last backslash is.
      Dim position As Integer = filepath.LastIndexOf("\"c)
      ' If there is no backslash, assume that this is a filename.
      If position = -1 Then
         ' Determine whether file exists in the current directory.
         If File.Exists(Environment.CurrentDirectory + Path.DirectorySeparatorChar + filepath) Then
            Return filepath
         Else
            Return String.Empty
         End If
      Else
         ' Determine whether file exists using filepath.
         If File.Exists(filepath) Then
            ' Return filename without file path.
            Return filepath.Substring(position + 1)
         Else
            Return String.Empty
         End If                     
      End If
   End Function
End Module 
' The example displays the following output:
'        delegate.txt

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Этот метод начинает поиск по последнему расположению этого экземпляра и продолжается к началу до тех пор, пока не будет найдена value, либо будет рассмотрена первая позиция символа. Поиск учитывает регистр.

Этот метод выполняет порядковый поиск (без учета языка и региональных параметров), где символ считается эквивалентным другому символу, только если их скалярные значения Юникода совпадают. Чтобы выполнить поиск с учетом языка и региональных параметров, используйте метод CompareInfo.LastIndexOf, где скалярное значение Юникода, представляющее предварительно скомпилированные символы, например ligature "Æ" (U+00C6), может считаться эквивалентным любому вхождлению компонентов символа в правильной последовательности, например "AE" (U+0041, U+0045) в зависимости от языка и региональных параметров.

См. также раздел

• Char
• IndexOf(Char)
• IndexOfAny(Char[])
• LastIndexOfAny(Char[])

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

Исходный код:

String.Searching.cs

public:
 int LastIndexOf(System::String ^ value, int startIndex);

public int LastIndexOf (string value, int startIndex);

member this.LastIndexOf : string * int -> int

Public Function LastIndexOf (value As String, startIndex As Integer) As Integer

Параметры

Возвращаемое значение

Отсчитываемое от нуля положение начального индекса value, если эта строка найдена или -1, если она не найдена или если текущий экземпляр равен Empty.

Исключения

Примеры

Следующий пример находит индекс всех вхождения строки в целевой строке, работая с конца целевой строки до начала целевой строки.

// Sample for String::LastIndexOf(String, Int32)
using namespace System;
int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
   String^ br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
   String^ str = "Now is the time for all good men to come to the aid of their party.";
   int start;
   int at;
   start = str->Length - 1;
   Console::WriteLine( "All occurrences of 'he' from position {0} to 0.", start );
   Console::WriteLine( "{0}\n{1}\n{2}\n", br1, br2, str );
   Console::Write( "The string 'he' occurs at position(s): " );
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      at = str->LastIndexOf( "he", start );
      if ( at > -1 )
      {
         Console::Write( " {0} ", at );
         start = at - 1;
      }
   }

   Console::WriteLine();
}

/*
This example produces the following results:
All occurrences of 'he' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s):  56  45  8
*/

// Sample for String.LastIndexOf(String, Int32)
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;

    start = str.Length-1;
    Console.WriteLine("All occurrences of 'he' from position {0} to 0.", start);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The string 'he' occurs at position(s): ");

    at = 0;
    while((start > -1) && (at > -1))
        {
        at = str.LastIndexOf("he", start);
        if (at > -1)
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 'he' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 56 45 8


*/

// Sample for String.LastIndexOf(String, Int32)
open System

let br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
let br2 = "0123456789012345678901234567890123456789012345678901234567890123456"
let str = "Now is the time for all good men to come to the aid of their party."

let mutable start = str.Length - 1
printfn $"All occurrences of 'he' from position {start} to 0." 
printfn $"{br1}{Environment.NewLine}{br2}{Environment.NewLine}{str}{Environment.NewLine}"
printf "The string 'he' occurs at position(s): "

let mutable at = 0
while (start > -1) && (at > -1) do
    at <- str.LastIndexOf("he", start)
    if at > -1 then
        printf $"{at} "
        start <- at - 1
printf $"{Environment.NewLine}{Environment.NewLine}{Environment.NewLine}"
(*
This example produces the following results:
All occurrences of 'he' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 56 45 8


*)

' Sample for String.LastIndexOf(String, Int32)
 _

Class Sample
   
   Public Shared Sub Main()
      
      Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
      Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
      Dim str As String = "Now is the time for all good men to come to the aid of their party."
      Dim start As Integer
      Dim at As Integer

      '#3
      start = str.Length - 1
      Console.WriteLine("All occurrences of 'he' from position {0} to 0.", start)
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The string 'he' occurs at position(s): ")
      
      at = 0
      While start > - 1 And at > - 1
         at = str.LastIndexOf("he", start)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 'he' from position 66 to 0.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The string 'he' occurs at position(s): 56 45 8
'
'

Комментарии

Нумерация индексов начинается с нуля. То есть первый символ в строке равен нулю индекса, а последний — Length – 1.

Поиск начинается с startIndex позиции символа этого экземпляра и продолжается назад к началу, пока не будет найдена value или была рассмотрена первая позиция символа. Например, если startIndexLength – 1, метод выполняет поиск каждого символа из последнего символа в строке до начала.

Этот метод выполняет поиск слова (с учетом регистра и языка и региональных параметров) с помощью текущего языка и региональных параметров.

Наборы символов включают игнорируемые символы, которые не учитываются при выполнении лингвистического или языка и региональных параметров. В поиске с учетом языка и региональных параметров, если value содержит игнорируемый символ, результат эквивалентен поиску с помощью этого символа. В следующем примере метод LastIndexOf(String, Int32) используется для поиска подстроки, включающей мягкий дефис (U+00AD), и который предшествует или включает окончательный "m" в строку. Если пример выполняется в .NET Framework 4 или более поздней версии, так как мягкий дефис в строке поиска игнорируется, вызывая метод для поиска подстроки, состоящей из мягкого дефиса и "m", возвращает позицию "m" в строке, в то время как вызывает ее для поиска подстроки, состоящей из мягкого дефиса и "n", возвращает положение "n".

int position = 0;
string s1 = "ani\u00ADmal";
string s2 = "animal";

// Find the index of the soft hyphen followed by "n".
position = s1.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s1.LastIndexOf("\u00ADn", position));

position = s2.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s2.LastIndexOf("\u00ADn", position));

// Find the index of the soft hyphen followed by "m".
position = s1.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s1.LastIndexOf("\u00ADm", position));

position = s2.LastIndexOf("m");
Console.WriteLine($"'m' at position {position}");

if (position >= 0)
    Console.WriteLine(s2.LastIndexOf("\u00ADm", position));

// The example displays the following output:
//
// 'm' at position 4
// 1
// 'm' at position 3
// 1
// 'm' at position 4
// 4
// 'm' at position 3
// 3

let s1 = "ani\u00ADmal"
let s2 = "animal"

// Find the index of the soft hyphen followed by "n".
let position = s1.LastIndexOf "m"
printfn $"'m' at position {position}"

if position >= 0 then
    printfn $"""{s1.LastIndexOf("\u00ADn", position)}"""

let position = s2.LastIndexOf "m"
printfn $"'m' at position {position}"

if position >= 0 then
    printfn $"""{s2.LastIndexOf("\u00ADn", position)}"""

// Find the index of the soft hyphen followed by "m".
let position = s1.LastIndexOf "m"
printfn $"'m' at position {position}"

if position >= 0 then
    printfn $"""{s1.LastIndexOf("\u00ADm", position)}"""

let position = s2.LastIndexOf "m"
printfn $"'m' at position {position}"

if position >= 0 then
    printfn $"""{s2.LastIndexOf("\u00ADm", position)}"""
// The example displays the following output:
//
// 'm' at position 4
// 1
// 'm' at position 3
// 1
// 'm' at position 4
// 4
// 'm' at position 3
// 3

Dim position As Integer
Dim softHyphen As String = ChrW(&HAD)
Dim s1 As String = "ani" + softHyphen + "mal"
Dim s2 As String = "animal"

' Find the index of the soft hyphen followed by "n".
position = s1.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s1.LastIndexOf(softHyphen + "n", position))
End If

position = s2.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s2.LastIndexOf(softHyphen + "n", position))
End If

' Find the index of the soft hyphen followed by "m".
position = s1.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s1.LastIndexOf(softHyphen + "m", position))
End If

position = s2.LastIndexOf("m")
Console.WriteLine($"'m' at position {position}")

If position >= 0 Then
    Console.WriteLine(s2.LastIndexOf(softHyphen + "m", position))
End If

' The example displays the following output:
'
' 'm' at position 4
' 1
' 'm' at position 3
' 1
' 'm' at position 4
' 4
' 'm' at position 3
' 3

Примечания для тех, кто вызывает этот метод

Как описано в рекомендации по использованию строк, рекомендуется избегать вызова методов сравнения строк, заменяющих значения по умолчанию и вызывающих методы, требующие явного указания параметров. Чтобы найти индекс подстроки, которая предшествует определенной позиции символа, используя правила сравнения текущего языка и региональных параметров, явно сообщите о намерении путем вызова перегрузки метода LastIndexOf(String, Int32, StringComparison) значением CurrentCulture для параметра comparisonType. Если вам не требуется лингвистическое сравнение, рассмотрите возможность использования Ordinal.

См. также раздел

• Int32
• IndexOf(Char)
• IndexOfAny(Char[])
• LastIndexOfAny(Char[])