Queryable.OfType<TResult>(IQueryable) メソッド

定義

指定された型に基づいて IQueryable の要素をフィルター処理します。Filters the elements of an IQueryable based on a specified type.

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)

型パラメーター

TResult

シーケンスの要素をフィルター処理する型。The type to filter the elements of the sequence on.

パラメーター

source
IQueryable

フィルター処理する要素を含む IQueryableAn IQueryable whose elements to filter.

戻り値

IQueryable<TResult>

source 型を持つ、TResult の要素を含むコレクション。A collection that contains the elements from source that have type TResult.

例外

sourcenull です。source is null.

次のコード例では、OfType を使用して MemberInfo型の要素のリストから PropertyInfo 型ではない要素をフィルターで除外する方法を示します。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

注釈

OfType メソッドは、構築されたジェネリックメソッドとしての呼び出し OfType 自体を表す MethodCallExpression を生成します。The OfType method generates a MethodCallExpression that represents calling OfType itself as a constructed generic method. 次に、source パラメーターの Provider プロパティによって表される IQueryProviderCreateQuery(Expression) メソッドに MethodCallExpression を渡します。It then passes the MethodCallExpression to the CreateQuery(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

OfType の呼び出しを表す式ツリーを実行した結果として発生するクエリ動作は、source パラメーターの型の実装によって異なります。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. 期待される動作は、TResult型ではない source 内の要素をフィルターで除外することです。The expected behavior is that it filters out any elements in source that are not of type TResult.

適用対象