Enumerable.AsEnumerable<TSource>(IEnumerable<TSource>) Méthode

Définition

Retourne l’entrée typée comme IEnumerable<T>.Returns the input typed as IEnumerable<T>.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ AsEnumerable(System::Collections::Generic::IEnumerable<TSource> ^ source);
public static System.Collections.Generic.IEnumerable<TSource> AsEnumerable<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);
static member AsEnumerable : seq<'Source> -> seq<'Source>
<Extension()>
Public Function AsEnumerable(Of TSource) (source As IEnumerable(Of TSource)) As IEnumerable(Of TSource)

Paramètres de type

TSource

Le type des éléments de source.The type of the elements of source.

Paramètres

source
IEnumerable<TSource>

Séquence à saisir comme IEnumerable<T>.The sequence to type as IEnumerable<T>.

Retours

IEnumerable<TSource>

Séquence d'entrées typées comme IEnumerable<T>.The input sequence typed as IEnumerable<T>.

Exemples

L’exemple de code suivant montre comment utiliser AsEnumerable<TSource>(IEnumerable<TSource>) pour masquer la méthode personnalisée d’un type Where lorsque l’implémentation de l’opérateur de requête standard est souhaitée.The following code example demonstrates how to use AsEnumerable<TSource>(IEnumerable<TSource>) to hide a type's custom Where method when the standard query operator implementation is desired.

// Custom class.
class Clump<T> : List<T>
{
    // Custom implementation of Where().
    public IEnumerable<T> Where(Func<T, bool> predicate)
    {
        Console.WriteLine("In Clump's implementation of Where().");
        return Enumerable.Where(this, predicate);
    }
}

static void AsEnumerableEx1()
{
    // Create a new Clump<T> object.
    Clump<string> fruitClump =
        new Clump<string> { "apple", "passionfruit", "banana",
            "mango", "orange", "blueberry", "grape", "strawberry" };

    // First call to Where():
    // Call Clump's Where() method with a predicate.
    IEnumerable<string> query1 =
        fruitClump.Where(fruit => fruit.Contains("o"));

    Console.WriteLine("query1 has been created.\n");

    // Second call to Where():
    // First call AsEnumerable() to hide Clump's Where() method and thereby
    // force System.Linq.Enumerable's Where() method to be called.
    IEnumerable<string> query2 =
        fruitClump.AsEnumerable().Where(fruit => fruit.Contains("o"));

    // Display the output.
    Console.WriteLine("query2 has been created.");
}

// This code produces the following output:
//
// In Clump's implementation of Where().
// query1 has been created.
//
// query2 has been created.
Dim output As New System.Text.StringBuilder

' A custom class.
Class Clump(Of T)
    Inherits List(Of T)

    ' Constructor.
    Public Sub New(ByVal collection As IEnumerable(Of T))
        MyBase.New(collection)
    End Sub

    ' Custom implementation of Where().
    Function Where(ByVal predicate As Func(Of T, Boolean)) As IEnumerable(Of T)
        output.AppendLine("In Clump's implementation of Where().")
        Return Enumerable.Where(Me, predicate)
    End Function
End Class

Sub AsEnumerableEx1()
    ' Create a new Clump(Of T) object.
    Dim fruitClump As New Clump(Of String)(New String() _
                                       {"apple", "passionfruit", "banana",
                                        "mango", "orange", "blueberry",
                                        "grape", "strawberry"})

    ' First call to Where():
    ' Call Clump's Where() method with a predicate.
    Dim query1 As IEnumerable(Of String) =
    fruitClump.Where(Function(fruit) fruit.Contains("o"))
    output.AppendLine("query1 has been created." & vbCrLf)

    ' Second call to Where():
    ' First call AsEnumerable() to hide Clump's Where() method and thereby
    ' force System.Linq.Enumerable's Where() method to be called.
    Dim query2 As IEnumerable(Of String) =
    fruitClump.AsEnumerable().Where(Function(fruit) fruit.Contains("o"))
    output.AppendLine("query2 has been created.")

    ' Display the output.
    Console.WriteLine(output.ToString())
End Sub

' This code produces the following output:
'
' In Clump's implementation of Where().
' query1 has been created.
'
' query2 has been created.

Remarques

La AsEnumerable<TSource>(IEnumerable<TSource>) méthode n’a aucun effet que de modifier le type au moment de la compilation de source à partir d’un type qui implémente IEnumerable<T> sur IEnumerable<T> lui-même.The AsEnumerable<TSource>(IEnumerable<TSource>) method has no effect other than to change the compile-time type of source from a type that implements IEnumerable<T> to IEnumerable<T> itself.

AsEnumerable<TSource>(IEnumerable<TSource>) peut être utilisé pour choisir entre les implémentations de requête lorsqu’une séquence implémente IEnumerable<T> , mais également un ensemble différent de méthodes de requête publiques disponibles.AsEnumerable<TSource>(IEnumerable<TSource>) can be used to choose between query implementations when a sequence implements IEnumerable<T> but also has a different set of public query methods available. Par exemple, à partir d’une classe générique Table qui implémente IEnumerable<T> et possède ses propres méthodes telles que Where , Select et SelectMany , un appel à Where appelle la Where méthode publique de Table .For example, given a generic class Table that implements IEnumerable<T> and has its own methods such as Where, Select, and SelectMany, a call to Where would invoke the public Where method of Table. Un Table type qui représente une table de base de données peut avoir une Where méthode qui prend l’argument de prédicat comme une arborescence d’expression et convertit l’arborescence en SQL pour l’exécution distante.A Table type that represents a database table could have a Where method that takes the predicate argument as an expression tree and converts the tree to SQL for remote execution. Si l’exécution à distance n’est pas souhaitée, par exemple parce que le prédicat appelle une méthode locale, la AsEnumerable méthode peut être utilisée pour masquer les méthodes personnalisées et rendre les opérateurs de requête standard disponibles.If remote execution is not desired, for example because the predicate invokes a local method, the AsEnumerable method can be used to hide the custom methods and instead make the standard query operators available.

S’applique à