Gewusst wie: Zählen der Vorkommen eines Worts in einer Zeichenfolge (LINQ)
In diesem Beispiel wird gezeigt, wie mithilfe einer LINQ-Abfrage die Vorkommen eines angegebenen Worts in einer Zeichenfolge gezählt werden.Beachten Sie, dass für die Zählung zuerst die Split-Methode aufgerufen wird, um ein Array von Wörtern zu erstellen.Durch die Split-Methode wird die Leistung beeinträchtigt. Wenn Sie bei der Zeichenfolge nur die Wörter zählen möchten, sollten Sie stattdessen die Matches-Methode oder die IndexOf-Methode verwenden.Spielt die Leistung jedoch keine entscheidende Rolle oder haben Sie den Satz bereits unterteilt, um andere Arten von Abfragen auszuführen, ist es sinnvoll, mit LINQ auch die Wörter oder Begriffe zu zählen.
Beispiel
Class CountWords
Shared Sub Main()
Dim text As String = "Historically, the world of data and the world of objects" &
" have not been well integrated. Programmers work in C# or Visual Basic" &
" and also in SQL or XQuery. On the one side are concepts such as classes," &
" objects, fields, inheritance, and .NET Framework APIs. On the other side" &
" are tables, columns, rows, nodes, and separate languages for dealing with" &
" them. Data types often require translation between the two worlds; there are" &
" different standard functions. Because the object world has no notion of query, a" &
" query can only be represented as a string without compile-time type checking or" &
" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" &
" objects in memory is often tedious and error-prone."
Dim searchTerm As String = "data"
' Convert the string into an array of words.
Dim dataSource As String() = text.Split(New Char() {" ", ",", ".", ";", ":"},
StringSplitOptions.RemoveEmptyEntries)
' Create and execute the query. It executes immediately
' because a singleton value is produced.
' Use ToLower to match "data" and "Data"
Dim matchQuery = From word In dataSource
Where word.ToLowerInvariant() = searchTerm.ToLowerInvariant()
Select word
' Count the matches.
Dim count As Integer = matchQuery.Count()
Console.WriteLine(count & " occurrence(s) of the search term """ &
searchTerm & """ were found.")
' Keep console window open in debug mode.
Console.WriteLine("Press any key to exit.")
Console.ReadKey()
End Sub
End Class
' Output:
' 3 occurrence(s) of the search term "data" were found.
class CountWords
{
static void Main()
{
string text = @"Historically, the world of data and the world of objects" +
@" have not been well integrated. Programmers work in C# or Visual Basic" +
@" and also in SQL or XQuery. On the one side are concepts such as classes," +
@" objects, fields, inheritance, and .NET Framework APIs. On the other side" +
@" are tables, columns, rows, nodes, and separate languages for dealing with" +
@" them. Data types often require translation between the two worlds; there are" +
@" different standard functions. Because the object world has no notion of query, a" +
@" query can only be represented as a string without compile-time type checking or" +
@" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" +
@" objects in memory is often tedious and error-prone.";
string searchTerm = "data";
//Convert the string into an array of words
string[] source = text.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' }, StringSplitOptions.RemoveEmptyEntries);
// Create and execute the query. It executes immediately
// because a singleton value is produced.
// Use ToLowerInvariant to match "data" and "Data"
var matchQuery = from word in source
where word.ToLowerInvariant() == searchTerm.ToLowerInvariant()
select word;
// Count the matches.
int wordCount = matchQuery.Count();
Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.", wordCount, searchTerm);
// Keep console window open in debug mode
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
}
/* Output:
3 occurrences(s) of the search term "data" were found.
*/
Kompilieren des Codes
Erstellen Sie ein Visual Studio-Projekt für die .NET Framework-Version 3.5.Standardmäßig weist das Projekt einen Verweis auf System.Core.dll und eine using-Direktive (C#) oder eine Imports-Anweisung (Visual Basic) für den System.Linq-Namespace auf.Fügen Sie in C#-Projekten eine using-Direktive für den System.IO-Namespace hinzu.
Kopieren Sie diesen Code ins Projekt.
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