Queryable.OfType<TResult>(IQueryable) Méthode

public:
generic <typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IQueryable<TResult> ^ OfType(System::Linq::IQueryable ^ source);

public static System.Linq.IQueryable<TResult> OfType<TResult> (this System.Linq.IQueryable source);

static member OfType : System.Linq.IQueryable -> System.Linq.IQueryable<'Result>

<Extension()>
Public Function OfType(Of TResult) (source As IQueryable) As IQueryable(Of TResult)

Paramètres de type

Paramètres

Retours

IQueryable<TResult>

Collection qui contient les éléments de source qui ont le type TResult.A collection that contains the elements from source that have type TResult.

Exceptions

Exemples

L’exemple de code suivant montre comment utiliser OfType pour filtrer les éléments qui ne sont pas de type PropertyInfo dans une liste d’éléments de type MemberInfo .The following code example demonstrates how to use OfType to filter out elements that are not of type PropertyInfo from a list of elements of type MemberInfo.

// Create a list of MemberInfo objects.
List<System.Reflection.MemberInfo> members = typeof(String).GetMembers().ToList();

// Return only those items that can be cast to type PropertyInfo.
IQueryable<System.Reflection.PropertyInfo> propertiesOnly =
    members.AsQueryable().OfType<System.Reflection.PropertyInfo>();

Console.WriteLine("Members of type 'PropertyInfo' are:");
foreach (System.Reflection.PropertyInfo pi in propertiesOnly)
    Console.WriteLine(pi.Name);

/*
    This code produces the following output:

    Members of type 'PropertyInfo' are:
    Chars
    Length
*/

' Create a list of MemberInfo objects.
Dim members As List(Of System.Reflection.MemberInfo) = GetType(String).GetMembers().ToList()

' Return only those items that can be cast to type PropertyInfo.
Dim propertiesOnly As IQueryable(Of System.Reflection.PropertyInfo) = _
        members.AsQueryable().OfType(Of System.Reflection.PropertyInfo)()

Dim output As New System.Text.StringBuilder
output.AppendLine("Members of type 'PropertyInfo' are:")
For Each pi As System.Reflection.PropertyInfo In propertiesOnly
    output.AppendLine(pi.Name)
Next

' Display the output.
MsgBox(output.ToString())

' This code produces the following output:

' Members of type 'PropertyInfo' are:
' Chars
' Length

Remarques

La OfType méthode génère un MethodCallExpression qui représente l’appel de OfType lui-même comme une méthode générique construite.The OfType method generates a MethodCallExpression that represents calling OfType itself as a constructed generic method. Il passe ensuite MethodCallExpression à la CreateQuery(Expression) méthode de IQueryProvider représenté par la Provider propriété du source paramètre.It then passes the MethodCallExpression to the CreateQuery(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

Le comportement de la requête qui se produit suite à l’exécution d’une arborescence d’expressions qui représente l’appel de OfType dépend de l’implémentation du type du source paramètre.The query behavior that occurs as a result of executing an expression tree that represents calling OfType depends on the implementation of the type of the source parameter. Le comportement attendu est qu’il filtre tous les éléments de source qui ne sont pas de type TResult .The expected behavior is that it filters out any elements in source that are not of type TResult.

S’applique à