String.StartsWith Метод

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

public:
 bool StartsWith(System::String ^ value, bool ignoreCase, System::Globalization::CultureInfo ^ culture);

public bool StartsWith (string value, bool ignoreCase, System.Globalization.CultureInfo? culture);

public bool StartsWith (string value, bool ignoreCase, System.Globalization.CultureInfo culture);

member this.StartsWith : string * bool * System.Globalization.CultureInfo -> bool

Public Function StartsWith (value As String, ignoreCase As Boolean, culture As CultureInfo) As Boolean

Параметры

Возвращаемое значение

true, если параметр value соответствует началу данной строки; в противном случае — false.

Исключения

Примеры

В следующем примере определяется, встречается ли строка в начале другой строки. Метод StartsWith вызывается несколько раз с учетом регистра, учетом регистра и различными языками и региональными параметрами, влияющими на результаты поиска.

// This code example demonstrates the 
// System.String.StartsWith(String, ..., CultureInfo) method.

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

class Sample 
{
    public static void Main() 
    {
    string msg1 = "Search for the target string \"{0}\" in the string \"{1}\".\n";
    string msg2 = "Using the {0} - \"{1}\" culture:";
    string msg3 = "  The string to search ends with the target string: {0}";
    bool result = false;
    CultureInfo ci;

// Define a target string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string capitalARing = "\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 aRingXYZ = "\u0061\u030a" + "xyz";

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

// Display the string to search for and the string to search.
    Console.WriteLine(msg1, capitalARing, aRingXYZ);

// Search using English-United States culture.
    ci = new CultureInfo("en-US");
    Console.WriteLine(msg2, ci.DisplayName, ci.Name);

    Console.WriteLine("Case sensitive:");
    result = aRingXYZ.StartsWith(capitalARing, false, ci);
    Console.WriteLine(msg3, result);

    Console.WriteLine("Case insensitive:");
    result = aRingXYZ.StartsWith(capitalARing, true, ci);
    Console.WriteLine(msg3, result);
    Console.WriteLine();

// Search using Swedish-Sweden culture.
    ci = new CultureInfo("sv-SE");
    Console.WriteLine(msg2, ci.DisplayName, ci.Name);

    Console.WriteLine("Case sensitive:");
    result = aRingXYZ.StartsWith(capitalARing, false, ci);
    Console.WriteLine(msg3, result);

    Console.WriteLine("Case insensitive:");
    result = aRingXYZ.StartsWith(capitalARing, true, ci);
    Console.WriteLine(msg3, result);
    }
}

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

Search for the target string "Å" in the string "a°xyz".

Using the English (United States) - "en-US" culture:
Case sensitive:
  The string to search ends with the target string: False
Case insensitive:
  The string to search ends with the target string: True

Using the Swedish (Sweden) - "sv-SE" culture:
Case sensitive:
  The string to search ends with the target string: False
Case insensitive:
  The string to search ends with the target string: False

*/

// This code example demonstrates the
// System.String.StartsWith(String, ..., CultureInfo) method.

open System
open System.Globalization
 
[<EntryPoint>]
let main _ =
    let msg1 = "Search for the target string \"{0}\" in the string \"{1}\".\n"
    let msg2 = "Using the {0} - \"{1}\" culture:"
    let msg3 = "  The string to search ends with the target string: {0}"

    // Define a target string to search for.
    // U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    let capitalARing = "\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 aRingXYZ = "\u0061\u030a" + "xyz"

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

    // Display the string to search for and the string to search.
    Console.WriteLine(msg1, capitalARing, aRingXYZ)

    // Search using English-United States culture.
    let ci = CultureInfo "en-US"
    Console.WriteLine(msg2, ci.DisplayName, ci.Name)

    printfn "Case sensitive:"
    let result = aRingXYZ.StartsWith(capitalARing, false, ci)
    Console.WriteLine(msg3, result)

    printfn "Case insensitive:"
    let result = aRingXYZ.StartsWith(capitalARing, true, ci)
    Console.WriteLine(msg3, result)
    printfn ""

    // Search using Swedish-Sweden culture.
    let ci = CultureInfo "sv-SE"
    Console.WriteLine(msg2, ci.DisplayName, ci.Name)

    printfn "Case sensitive:"
    let result = aRingXYZ.StartsWith(capitalARing, false, ci)
    Console.WriteLine(msg3, result)

    printfn "Case insensitive:"
    let result = aRingXYZ.StartsWith(capitalARing, true, ci)
    Console.WriteLine(msg3, result)
    0
(*
Note: This code example was executed on a console whose user interface
culture is "en-US" (English-United States).

Search for the target string "Å" in the string "a°xyz".

Using the English (United States) - "en-US" culture:
Case sensitive:
  The string to search ends with the target string: False
Case insensitive:
  The string to search ends with the target string: True

Using the Swedish (Sweden) - "sv-SE" culture:
Case sensitive:
  The string to search ends with the target string: False
Case insensitive:
  The string to search ends with the target string: False

*)

' This code example demonstrates the 
' System.String.StartsWith(String, ..., CultureInfo) method.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim msg1 As String = "Search for the target string ""{0}"" in the string ""{1}""." & vbCrLf
        Dim msg2 As String = "Using the {0} - ""{1}"" culture:"
        Dim msg3 As String = "  The string to search ends with the target string: {0}"
        Dim result As Boolean = False
        Dim ci As CultureInfo
        
        ' Define a target string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim capitalARing 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 aRingXYZ As String = "å" & "xyz"
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        
        ' Display the string to search for and the string to search.
        Console.WriteLine(msg1, capitalARing, aRingXYZ)
        
        ' Search using English-United States culture.
        ci = New CultureInfo("en-US")
        Console.WriteLine(msg2, ci.DisplayName, ci.Name)
        
        Console.WriteLine("Case sensitive:")
        result = aRingXYZ.StartsWith(capitalARing, False, ci)
        Console.WriteLine(msg3, result)
        
        Console.WriteLine("Case insensitive:")
        result = aRingXYZ.StartsWith(capitalARing, True, ci)
        Console.WriteLine(msg3, result)
        Console.WriteLine()
        
        ' Search using Swedish-Sweden culture.
        ci = New CultureInfo("sv-SE")
        Console.WriteLine(msg2, ci.DisplayName, ci.Name)
        
        Console.WriteLine("Case sensitive:")
        result = aRingXYZ.StartsWith(capitalARing, False, ci)
        Console.WriteLine(msg3, result)
        
        Console.WriteLine("Case insensitive:")
        result = aRingXYZ.StartsWith(capitalARing, True, ci)
        Console.WriteLine(msg3, result)
    
    End Sub
End Class

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'Search for the target string "Å" in the string "a°xyz".
'
'Using the English (United States) - "en-US" culture:
'Case sensitive:
'  The string to search ends with the target string: False
'Case insensitive:
'  The string to search ends with the target string: True
'
'Using the Swedish (Sweden) - "sv-SE" culture:
'Case sensitive:
'  The string to search ends with the target string: False
'Case insensitive:
'  The string to search ends with the target string: False
'

Комментарии

Этот метод сравнивает value параметр с подстрокой в начале строки, которая имеет ту же длину value, что и , и возвращает значение, указывающее, равны ли они. Чтобы быть равным, value должен быть пустой строкой (String.Empty), должен быть ссылкой на этот же экземпляр или должен соответствовать началу этого экземпляра.

Этот метод выполняет сравнение с использованием указанного регистра и языка и региональных параметров.

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

public:
 bool StartsWith(System::String ^ value, StringComparison comparisonType);

public bool StartsWith (string value, StringComparison comparisonType);

[System.Runtime.InteropServices.ComVisible(false)]
public bool StartsWith (string value, StringComparison comparisonType);

member this.StartsWith : string * StringComparison -> bool

[<System.Runtime.InteropServices.ComVisible(false)>]
member this.StartsWith : string * StringComparison -> bool

Public Function StartsWith (value As String, comparisonType As StringComparison) As Boolean

Параметры

Возвращаемое значение

Значение true, если данный экземпляр начинается со значения value; в противном случае — значение false.

Атрибуты

ComVisibleAttribute

Исключения

Примеры

В следующем примере выполняется поиск строки "the" в начале более длинной строки, которая начинается со слова "The". Как показано в выходных данных примера, вызов StartsWith(String, StringComparison) метода , который выполняет сравнение без учета языка и региональных параметров, но с учетом регистра, не соответствует строке, а вызов, выполняющий сравнение без учета языка и региональных параметров и регистра, соответствует строке.

using namespace System;

void main()
{
   String^ title = "The House of the Seven Gables";
   String^ searchString = "the";
   StringComparison comparison = StringComparison::InvariantCulture;
   Console::WriteLine("'{0}':", title);
   Console::WriteLine("   Starts with '{0}' ({1:G} comparison): {2}",
                      searchString, comparison,
                      title->StartsWith(searchString, comparison));

   comparison = StringComparison::InvariantCultureIgnoreCase;
   Console::WriteLine("   Starts with '{0}' ({1:G} comparison): {2}",
                      searchString, comparison,
                      title->StartsWith(searchString, comparison));
   }
// The example displays the following output:
//       'The House of the Seven Gables':
//          Starts with 'the' (InvariantCulture comparison): False
//          Starts with 'the' (InvariantCultureIgnoreCase comparison): True

using System;

public class Example
{
   public static void Main()
   {
      String title = "The House of the Seven Gables";
      String searchString = "the";
      StringComparison comparison = StringComparison.InvariantCulture;
      Console.WriteLine("'{0}':", title);
      Console.WriteLine("   Starts with '{0}' ({1:G} comparison): {2}",
                        searchString, comparison,
                        title.StartsWith(searchString, comparison));

      comparison = StringComparison.InvariantCultureIgnoreCase;
      Console.WriteLine("   Starts with '{0}' ({1:G} comparison): {2}",
                        searchString, comparison,
                        title.StartsWith(searchString, comparison));
   }
}
// The example displays the following output:
//       'The House of the Seven Gables':
//          Starts with 'the' (InvariantCulture comparison): False
//          Starts with 'the' (InvariantCultureIgnoreCase comparison): True

open System

let title = "The House of the Seven Gables"
let searchString = "the"
let comparison = StringComparison.InvariantCulture
printfn $"'{title}':"
printfn $"   Starts with '{searchString}' ({comparison:G} comparison): {title.StartsWith(searchString, comparison)}"

let comparison2 = StringComparison.InvariantCultureIgnoreCase
printfn $"   Starts with '{searchString}' ({comparison2:G} comparison): {title.StartsWith(searchString, comparison2)}"
// The example displays the following output:
//       'The House of the Seven Gables':
//          Starts with 'the' (InvariantCulture comparison): False
//          Starts with 'the' (InvariantCultureIgnoreCase comparison): True

Module Example
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim searchString As String = "the"
      Dim comparison As StringComparison = StringComparison.InvariantCulture
      Console.WriteLine("'{0}':", title)
      Console.WriteLine("   Starts with '{0}' ({1:G} comparison): {2}",
                        searchString, comparison,
                        title.StartsWith(searchString, comparison))

      comparison = StringComparison.InvariantCultureIgnoreCase
      Console.WriteLine("   Starts with '{0}' ({1:G} comparison): {2}",
                        searchString, comparison,
                        title.StartsWith(searchString, comparison))
   End Sub
End Module
' The example displays the following output:
'    'The House of the Seven Gables':
'       Starts with 'the' (InvariantCulture comparison): False
'       Starts with 'the' (InvariantCultureIgnoreCase comparison): True

В следующем примере определяется, начинается ли строка с определенной подстроки. Он инициализирует двумерный строковый массив. Первый элемент во втором измерении содержит строку, а второй — строку для поиска в начале первой строки. На результаты влияет выбор языка и региональных параметров, игнорируется ли регистр и выполняется порядковый номер сравнения. Обратите внимание, что если экземпляр строки содержит лигатуру, сравнения с учетом языка и региональных параметров с его последовательными символами успешно совпадают.

using namespace System;

void main()
{
   array<String^, 2>^ strings = gcnew array<String^, 2> { {"ABCdef", "abc" },                    
                         {"ABCdef", "abc" }, {"œil","oe" }, 
                         { "læring}", "lae" } };
   for (int ctr1 = strings->GetLowerBound(0); ctr1 <= strings->GetUpperBound(0); ctr1++)
   {
         for each (String^ cmpName in Enum::GetNames(StringComparison::typeid))
         { 
            StringComparison strCmp = (StringComparison) Enum::Parse(StringComparison::typeid, 
                                                         cmpName);
            String^ instance = strings[ctr1, 0];
            String^ value = strings[ctr1, 1];
            Console::WriteLine("{0} starts with {1}: {2} ({3} comparison)", 
                               instance, value, 
                               instance->StartsWith(value, strCmp), 
                               strCmp); 
         }
         Console::WriteLine();   
   }   
}

// The example displays the following output:
//       ABCdef starts with abc: False (CurrentCulture comparison)
//       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (InvariantCulture comparison)
//       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (Ordinal comparison)
//       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
//       
//       ABCdef starts with abc: False (CurrentCulture comparison)
//       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (InvariantCulture comparison)
//       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (Ordinal comparison)
//       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
//       
//       œil starts with oe: True (CurrentCulture comparison)
//       œil starts with oe: True (CurrentCultureIgnoreCase comparison)
//       œil starts with oe: True (InvariantCulture comparison)
//       œil starts with oe: True (InvariantCultureIgnoreCase comparison)
//       œil starts with oe: False (Ordinal comparison)
//       œil starts with oe: False (OrdinalIgnoreCase comparison)
//       
//       læring} starts with lae: True (CurrentCulture comparison)
//       læring} starts with lae: True (CurrentCultureIgnoreCase comparison)
//       læring} starts with lae: True (InvariantCulture comparison)
//       læring} starts with lae: True (InvariantCultureIgnoreCase comparison)
//       læring} starts with lae: False (Ordinal comparison)
//       læring} starts with lae: False (OrdinalIgnoreCase comparison)

using System;

public class Example
{
   public static void Main()
   {
      string[,] strings = { {"ABCdef", "abc" },                    
                            {"ABCdef", "abc" },  
                            {"œil","oe" },
                            { "læring}", "lae" } };
      for (int ctr1 = strings.GetLowerBound(0); ctr1 <= strings.GetUpperBound(0); ctr1++)
      {
            foreach (string cmpName in Enum.GetNames(typeof(StringComparison)))
            { 
               StringComparison strCmp = (StringComparison) Enum.Parse(typeof(StringComparison), 
                                                      cmpName);
               string instance = strings[ctr1, 0];
               string value = strings[ctr1, 1];
               Console.WriteLine("{0} starts with {1}: {2} ({3} comparison)", 
                                 instance, value, 
                                 instance.StartsWith(value, strCmp), 
                                 strCmp); 
            }
            Console.WriteLine();   
      }   
   }
}
// The example displays the following output:
//       ABCdef starts with abc: False (CurrentCulture comparison)
//       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (InvariantCulture comparison)
//       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (Ordinal comparison)
//       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
//       
//       ABCdef starts with abc: False (CurrentCulture comparison)
//       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (InvariantCulture comparison)
//       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (Ordinal comparison)
//       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
//       
//       œil starts with oe: True (CurrentCulture comparison)
//       œil starts with oe: True (CurrentCultureIgnoreCase comparison)
//       œil starts with oe: True (InvariantCulture comparison)
//       œil starts with oe: True (InvariantCultureIgnoreCase comparison)
//       œil starts with oe: False (Ordinal comparison)
//       œil starts with oe: False (OrdinalIgnoreCase comparison)
//       
//       læring} starts with lae: True (CurrentCulture comparison)
//       læring} starts with lae: True (CurrentCultureIgnoreCase comparison)
//       læring} starts with lae: True (InvariantCulture comparison)
//       læring} starts with lae: True (InvariantCultureIgnoreCase comparison)
//       læring} starts with lae: False (Ordinal comparison)
//       læring} starts with lae: False (OrdinalIgnoreCase comparison)

open System

let strings =
    array2D 
      [ [ "ABCdef"; "abc" ]
        [ "ABCdef"; "abc" ]
        [ "œil"; "oe" ]
        [ "læring}"; "lae" ] ]

for ctr1 = strings.GetLowerBound 0 to strings.GetUpperBound 0 do
    for cmpName in Enum.GetNames typeof<StringComparison> do
        let strCmp = Enum.Parse(typeof<StringComparison>, cmpName) :?> StringComparison
        let instance = strings[ctr1, 0]
        let value = strings[ctr1, 1]
        printfn $"{instance} starts with {value}: {instance.StartsWith(value, strCmp)} ({strCmp} comparison)"
    printfn ""
// The example displays the following output:
//       ABCdef starts with abc: False (CurrentCulture comparison)
//       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (InvariantCulture comparison)
//       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (Ordinal comparison)
//       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
//
//       ABCdef starts with abc: False (CurrentCulture comparison)
//       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (InvariantCulture comparison)
//       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
//       ABCdef starts with abc: False (Ordinal comparison)
//       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
//
//       œil starts with oe: True (CurrentCulture comparison)
//       œil starts with oe: True (CurrentCultureIgnoreCase comparison)
//       œil starts with oe: True (InvariantCulture comparison)
//       œil starts with oe: True (InvariantCultureIgnoreCase comparison)
//       œil starts with oe: False (Ordinal comparison)
//       œil starts with oe: False (OrdinalIgnoreCase comparison)
//
//       læring} starts with lae: True (CurrentCulture comparison)
//       læring} starts with lae: True (CurrentCultureIgnoreCase comparison)
//       læring} starts with lae: True (InvariantCulture comparison)
//       læring} starts with lae: True (InvariantCultureIgnoreCase comparison)
//       læring} starts with lae: False (Ordinal comparison)
//       læring} starts with lae: False (OrdinalIgnoreCase comparison)

Module Example
   Public Sub Main()
      Dim strings(,) As String = { {"ABCdef", "abc" },                    
                                   {"ABCdef", "abc" },  
                                   {"œil","oe" },
                                   { "læring}", "lae" } }
      For ctr1 As Integer = strings.GetLowerBound(0) To strings.GetUpperBound(0)
            For Each cmpName As String In [Enum].GetNames(GetType(StringComparison)) 
               Dim strCmp As StringComparison = CType([Enum].Parse(GetType(StringComparison), 
                                                      cmpName), StringComparison)
               Dim instance As String = strings(ctr1, 0)
               Dim value As String = strings(ctr1, 1)
               Console.WriteLine("{0} starts with {1}: {2} ({3} comparison)", 
                                 instance, value, 
                                 instance.StartsWith(value, strCmp), 
                                 strCmp) 
            Next
            Console.WriteLine()   
      Next   
   End Sub
End Module
' The example displays the following output:
'       ABCdef starts with abc: False (CurrentCulture comparison)
'       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
'       ABCdef starts with abc: False (InvariantCulture comparison)
'       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
'       ABCdef starts with abc: False (Ordinal comparison)
'       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
'       
'       ABCdef starts with abc: False (CurrentCulture comparison)
'       ABCdef starts with abc: True (CurrentCultureIgnoreCase comparison)
'       ABCdef starts with abc: False (InvariantCulture comparison)
'       ABCdef starts with abc: True (InvariantCultureIgnoreCase comparison)
'       ABCdef starts with abc: False (Ordinal comparison)
'       ABCdef starts with abc: True (OrdinalIgnoreCase comparison)
'       
'       œil starts with oe: True (CurrentCulture comparison)
'       œil starts with oe: True (CurrentCultureIgnoreCase comparison)
'       œil starts with oe: True (InvariantCulture comparison)
'       œil starts with oe: True (InvariantCultureIgnoreCase comparison)
'       œil starts with oe: False (Ordinal comparison)
'       œil starts with oe: False (OrdinalIgnoreCase comparison)
'       
'       læring} starts with lae: True (CurrentCulture comparison)
'       læring} starts with lae: True (CurrentCultureIgnoreCase comparison)
'       læring} starts with lae: True (InvariantCulture comparison)
'       læring} starts with lae: True (InvariantCultureIgnoreCase comparison)
'       læring} starts with lae: False (Ordinal comparison)
'       læring} starts with lae: False (OrdinalIgnoreCase comparison)

Комментарии

Метод StartsWith сравнивает value параметр с подстрокой в начале этой строки и возвращает значение, указывающее, равны ли они. Чтобы быть равным, value должен быть ссылкой на эту же строку, должен быть пустой строкой (""), или должен соответствовать началу этой строки. Тип сравнения, выполняемого методом , StartsWith зависит от значения comparisonType параметра . Сравнение может использовать соглашения текущего языка и региональных параметров (StringComparison.CurrentCulture и StringComparison.CurrentCultureIgnoreCase) или инвариантного языка и региональных параметров (StringComparison.InvariantCulture и StringComparison.InvariantCultureIgnoreCase) или может состоять из сравнения символов кодовых точек (StringComparison.Ordinal или StringComparison.OrdinalIgnoreCase). Сравнение также может быть с учетом регистра (StringComparison.CurrentCulture, , или StringComparison.Ordinal) или пропускать регистр (StringComparison.CurrentCultureIgnoreCase, StringComparison.InvariantCultureIgnoreCase, StringComparison.OrdinalIgnoreCaseStringComparison.InvariantCulture).

См. также раздел

• StringComparison

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

public:
 bool StartsWith(char value);

public bool StartsWith (char value);

member this.StartsWith : char -> bool

Public Function StartsWith (value As Char) As Boolean

Параметры

Возвращаемое значение

Значение true, если параметр value соответствует началу данной строки; в противном случае — значение false.

Комментарии

Этот метод выполняет порядковый номер (с учетом регистра и без учета языка и региональных параметров).

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

Исходный код:

String.Comparison.cs

public:
 bool StartsWith(System::String ^ value);

public bool StartsWith (string value);

member this.StartsWith : string -> bool

Public Function StartsWith (value As String) As Boolean

Параметры

Возвращаемое значение

Значение true, если параметр value соответствует началу данной строки; в противном случае — значение false.

Исключения

Примеры

В следующем примере определяется StripStartTags метод , который использует StartsWith(String) метод для удаления начальных тегов HTML из начала строки. Обратите внимание, что StripStartTags метод вызывается рекурсивно, чтобы гарантировать удаление нескольких начальных тегов HTML в начале строки. В этом примере не удаляются html-теги, внедренные в строку.

using namespace System;

String^ StripStartTags( String^ item )
{
   // Determine whether a tag begins the string.
   if (item->Trim()->StartsWith("<")) {
      // Find the closing tag.
      int lastLocation = item->IndexOf(">");
      
      // Remove the tag.
      if ( lastLocation >= 0 ) {
         item = item->Substring(lastLocation+ 1);
            
         // Remove any additional starting tags.
         item = StripStartTags(item);
      }      
   }

   return item;
}

int main()
{
   array<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 simply begins with a lesser than symbol, it should not be modified" };
   
   // Display the initial string array.
   Console::WriteLine("The original strings:");
   Console::WriteLine("---------------------");
   for each (String^ s in strSource)    
      Console::WriteLine( s );
   Console::WriteLine();

   Console::WriteLine( "Strings after starting tags have been stripped:");
   Console::WriteLine( "-----------------------------------------------");
   
   // Display the strings with starting tags removed.
   for each (String^ s in strSource)
      Console::WriteLine(StripStartTags(s));
}
// The example displays the following output:
//    The original strings:
//    ---------------------
//    <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 simply begins with a lesser than symbol, it should not be modified
//    
//    Strings after starting tags have been stripped:
//    -----------------------------------------------
//    This is bold text</b>
//    This is large Text</H1>
//    This has multiple tags</font></i></b>
//    This has <i>embedded</i> tags.</b>
//    <This line simply begins with a lesser than symbol, it should not be modified

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 simply begins with a lesser than symbol, it should not be modified" };

      // Display the initial string array.
      Console.WriteLine("The original strings:");
      Console.WriteLine("---------------------");
      foreach (var s in strSource)
         Console.WriteLine(s);
      Console.WriteLine();

      Console.WriteLine("Strings after starting tags have been stripped:");
      Console.WriteLine("-----------------------------------------------");

      // Display the strings with starting tags removed.
     foreach (var s in strSource)
        Console.WriteLine(StripStartTags(s));
   }

   private static string StripStartTags(string item)
   {
      // Determine whether a tag begins the string.
      if (item.Trim().StartsWith("<")) {
         // Find the closing tag.
         int lastLocation = item.IndexOf( ">" );
         // Remove the tag.
         if (lastLocation >= 0) {
            item =  item.Substring( lastLocation + 1 );

            // Remove any additional starting tags.
            item = StripStartTags(item);
         }
      }

      return item;
   }
}
// The example displays the following output:
//    The original strings:
//    ---------------------
//    <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 simply begins with a lesser than symbol, it should not be modified
//
//    Strings after starting tags have been stripped:
//    -----------------------------------------------
//    This is bold text</b>
//    This is large Text</H1>
//    This has multiple tags</font></i></b>
//    This has <i>embedded</i> tags.</b>
//    <This line simply begins with a lesser than symbol, it should not be modified

let rec stripStartTags (item: string) =
    // Determine whether a tag begins the string.
    if item.Trim().StartsWith "<" then
        // Find the closing tag.
        let lastLocation = item.IndexOf ">"
        // Remove the tag.
        let item = 
            if lastLocation >= 0 then
                item.Substring( lastLocation + 1 )
            else 
                item

        // Remove any additional starting tags.
        stripStartTags item
    else
        item

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 simply begins with a lesser than symbol, it should not be modified" |]

// Display the initial string array.
printfn "The original strings:"
printfn "---------------------"
for s in strSource do
    printfn $"{s}"
printfn ""

printfn "Strings after starting tags have been stripped:"
printfn "-----------------------------------------------"

// Display the strings with starting tags removed.
for s in strSource do
    printfn $"{stripStartTags s}"

// The example displays the following output:
//    The original strings:
//    ---------------------
//    <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 simply begins with a lesser than symbol, it should not be modified
//
//    Strings after starting tags have been stripped:
//    -----------------------------------------------
//    This is bold text</b>
//    This is large Text</H1>
//    This has multiple tags</font></i></b>
//    This has <i>embedded</i> tags.</b>
//    <This line simply begins with a lesser than symbol, it should not be modified

Public Class Example
   Public Shared 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 simply begins with a lesser than symbol, it should not be modified" }

      ' Display the initial string array.
      Console.WriteLine("The original strings:")
      Console.WriteLine("---------------------")
      For Each s In strSource
         Console.WriteLine(s)
      Next 
      Console.WriteLine()

      Console.WriteLine("Strings after starting tags have been stripped:")
      Console.WriteLine("-----------------------------------------------") 

      ' Display the strings with starting tags removed.
      For Each s In strSource
         Console.WriteLine(StripStartTags(s))
      Next 
   End Sub 

   Private Shared Function StripStartTags(item As String) As String
      ' Determine whether a tag begins the string.
      If item.Trim().StartsWith("<") Then
         ' Find the closing tag.
         Dim lastLocation As Integer = item.IndexOf(">")
         If lastLocation >= 0 Then
            ' Remove the tag.
            item = item.Substring((lastLocation + 1))
            
            ' Remove any additional starting tags.
            item = StripStartTags(item)
         End If
      End If
      
      Return item
   End Function 
End Class 
' The example displays the following output:
'    The original strings:
'    ---------------------
'    <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 simply begins with a lesser than symbol, it should not be modified
'    
'    Strings after starting tags have been stripped:
'    -----------------------------------------------
'    This is bold text</b>
'    This is large Text</H1>
'    This has multiple tags</font></i></b>
'    This has <i>embedded</i> tags.</b>
'    <This line simply begins with a lesser than symbol, it should not be modified

Комментарии

Этот метод сравнивает value подстроку в начале данного экземпляра, которая имеет ту же длину, что valueи , и возвращает значение, указывающее, равны ли они. Чтобы быть равным, value должен быть пустой строкой (String.Empty), должен быть ссылкой на этот же экземпляр или должен соответствовать началу этого экземпляра.

Этот метод выполняет сравнение слов (с учетом регистра и языка и региональных параметров) с использованием текущего языка и региональных параметров.

Примечания для тех, кто вызывает этот метод

Как описано в статье Рекомендации по использованию строк, рекомендуется избегать вызова методов сравнения строк, которые заменяют значения по умолчанию, и вместо этого вызывать методы, требующие явного указания параметров. Чтобы определить, начинается ли строка с определенной подстроки с помощью правил сравнения строк текущего языка и региональных параметров, явно сообщите о своем намерении, вызвав перегрузку StartsWith(String, StringComparison) метода со значением CurrentCulture для параметра comparisonType . Если вам не требуется лингвистическое сравнение, рассмотрите возможность использования Ordinal.

См. также раздел

• EndsWith(String)