Enumerable.Where Methode

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Where(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);

public static System.Collections.Generic.IEnumerable<TSource> Where<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);

static member Where : seq<'Source> * Func<'Source, bool> -> seq<'Source>

<Extension()>
Public Function Where(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As IEnumerable(Of TSource)

Typparameter

Parameter

Gibt zurück

IEnumerable<TSource>

Ein IEnumerable<T>, das Elemente aus der Eingabesequenz enthält, die die Bedingung erfüllenAn IEnumerable<T> that contains elements from the input sequence that satisfy the condition.

Ausnahmen

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie verwendet wird, Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) um eine Sequenz zu filtern.The following code example demonstrates how to use Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to filter a sequence.

List<string> fruits =
    new List<string> { "apple", "passionfruit", "banana", "mango",
                    "orange", "blueberry", "grape", "strawberry" };

IEnumerable<string> query = fruits.Where(fruit => fruit.Length < 6);

foreach (string fruit in query)
{
    Console.WriteLine(fruit);
}
/*
 This code produces the following output:

 apple
 mango
 grape
*/

' Create a list of strings.
Dim fruits As New List(Of String)(New String() _
                    {"apple", "passionfruit", "banana", "mango",
                     "orange", "blueberry", "grape", "strawberry"})

' Restrict the results to those strings whose 
' length is less than six.
Dim query As IEnumerable(Of String) =
fruits.Where(Function(fruit) fruit.Length < 6)

' Display the results.
Dim output As New System.Text.StringBuilder
For Each fruit As String In query
    output.AppendLine(fruit)
Next
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' apple
' mango
' grape

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst ausgeführt, wenn das Objekt durch Aufrufen der- GetEnumerator Methode direkt oder mithilfe von foreach in Visual c# oder in Visual Basic aufgezählt wird For Each .The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

In der Abfrage Ausdruckssyntax wird eine where (Visual c#)-oder Where (Visual Basic)-Klausel in einen Aufruf von übersetzt Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) .In query expression syntax, a where (Visual C#) or Where (Visual Basic) clause translates to an invocation of Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>).

Weitere Informationen

• where-Klausel (C#-Referenz)where clause (C# Reference)
• Where-Klausel (Visual Basic)Where Clause (Visual Basic)

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Where(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, int, bool> ^ predicate);

public static System.Collections.Generic.IEnumerable<TSource> Where<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,int,bool> predicate);

static member Where : seq<'Source> * Func<'Source, int, bool> -> seq<'Source>

<Extension()>
Public Function Where(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Integer, Boolean)) As IEnumerable(Of TSource)

Typparameter

Parameter

Gibt zurück

IEnumerable<TSource>

Ein IEnumerable<T>, das Elemente aus der Eingabesequenz enthält, die die Bedingung erfüllenAn IEnumerable<T> that contains elements from the input sequence that satisfy the condition.

Ausnahmen

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie verwendet wird, Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) um eine Sequenz auf der Grundlage eines Prädikats zu filtern, das den Index der einzelnen Elemente einschließt.The following code example demonstrates how to use Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) to filter a sequence based on a predicate that involves the index of each element.

int[] numbers = { 0, 30, 20, 15, 90, 85, 40, 75 };

IEnumerable<int> query =
    numbers.Where((number, index) => number <= index * 10);

foreach (int number in query)
{
    Console.WriteLine(number);
}
/*
 This code produces the following output:

 0
 20
 15
 40
*/

' Create an array of integers.
Dim numbers() As Integer = {0, 30, 20, 15, 90, 85, 40, 75}

' Restrict the results to those numbers whose
' values are less than or equal to their index times 10.
Dim query As IEnumerable(Of Integer) =
numbers.Where(Function(number, index) number <= index * 10)

' Display the results.
Dim output As New System.Text.StringBuilder
For Each number As Integer In query
    output.AppendLine(number)
Next
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' 0
' 20
' 15
' 40

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst ausgeführt, wenn das Objekt durch Aufrufen der- GetEnumerator Methode direkt oder mithilfe von foreach in Visual c# oder in Visual Basic aufgezählt wird For Each .The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

Das erste Argument von predicate stellt das zu testende Element dar.The first argument of predicate represents the element to test. Das zweite Argument stellt den NULL basierten Index des Elements innerhalb von dar source .The second argument represents the zero-based index of the element within source.