Func<T1,T2,T3,T4,TResult> 代理人

定義

generic <typename T1, typename T2, typename T3, typename T4, typename TResult>
public delegate TResult Func(T1 arg1, T2 arg2, T3 arg3, T4 arg4);

public delegate TResult Func<in T1,in T2,in T3,in T4,out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);

public delegate TResult Func<T1,T2,T3,T4,TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);

type Func<'T1, 'T2, 'T3, 'T4, 'Result> = delegate of 'T1 * 'T2 * 'T3 * 'T4 -> 'Result

Public Delegate Function Func(Of In T1, In T2, In T3, In T4, Out TResult)(arg1 As T1, arg2 As T2, arg3 As T3, arg4 As T4) As TResult 

Public Delegate Function Func(Of T1, T2, T3, T4, TResult)(arg1 As T1, arg2 As T2, arg3 As T3, arg4 As T4) As TResult 

型パラメーター

パラメーター

戻り値

TResult

このデリゲートによってカプセル化されるメソッドの戻り値。The return value of the method that this delegate encapsulates.

例

次の例は、デリゲートを宣言して使用する方法を示して Func<T1,T2,TResult> います。The following example demonstrates how to declare and use a Func<T1,T2,TResult> delegate. この例では、変数を宣言 Func<T1,T2,TResult> し、 String 値と Int32 値をパラメーターとして受け取るラムダ式を割り当てます。This example declares a Func<T1,T2,TResult> variable and assigns it a lambda expression that takes a String value and an Int32 value as parameters. trueパラメーターの長さ String がパラメーターの値と等しい場合、ラムダ式はを返し Int32 ます。The lambda expression returns true if the length of the String parameter is equal to the value of the Int32 parameter. その後、このメソッドをカプセル化するデリゲートは、文字列の配列内の文字列をフィルター処理するためにクエリで使用されます。The delegate that encapsulates this method is subsequently used in a query to filter strings in an array of strings.

using System;
using System.Collections.Generic;
using System.Linq;

public class Func3Example
{
   public static void Main()
   {
      Func<String, int, bool> predicate = (str, index) => str.Length == index;

      String[] words = { "orange", "apple", "Article", "elephant", "star", "and" };
      IEnumerable<String> aWords = words.Where(predicate).Select(str => str);

      foreach (String word in aWords)
         Console.WriteLine(word);
   }
}

Imports System.Collections.Generic
Imports System.Linq

Public Module Func3Example

   Public Sub Main()
      Dim predicate As Func(Of String, Integer, Boolean) = Function(str, index) str.Length = index

      Dim words() As String = { "orange", "apple", "Article", "elephant", "star", "and" }
      Dim aWords As IEnumerable(Of String) = words.Where(predicate)

      For Each word As String In aWords
         Console.WriteLine(word)
      Next   
   End Sub
End Module

注釈

このデリゲートを使用すると、カスタムデリゲートを明示的に宣言しなくてもパラメーターとして渡すことができるメソッドを表すことができます。You can use this delegate to represent a method that can be passed as a parameter without explicitly declaring a custom delegate. カプセル化されたメソッドは、このデリゲートで定義されているメソッドシグネチャに対応している必要があります。The encapsulated method must correspond to the method signature that is defined by this delegate. つまり、カプセル化されたメソッドには4つのパラメーターが必要であり、それぞれが値で渡され、値を返す必要があることを意味します。This means that the encapsulated method must have four parameters, each of which is passed to it by value, and that it must return a value.

デリゲートを使用する場合は Func<T1,T2,T3,T4,TResult> 、4つのパラメーターを持つメソッドをカプセル化するデリゲートを明示的に定義する必要はありません。When you use the Func<T1,T2,T3,T4,TResult> delegate, you do not have to explicitly define a delegate that encapsulates a method with four parameters. たとえば、次のコードでは、という汎用デリゲートを明示的に宣言 Searcher し、メソッドへの参照を IndexOf そのデリゲートインスタンスに割り当てています。For example, the following code explicitly declares a generic delegate named Searcher and assigns a reference to the IndexOf method to its delegate instance.

using System;

delegate int Searcher(string searchString, int start, int count,
                         StringComparison type);

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Searcher finder = title.IndexOf;
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters,
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.",
                              position, title);
         }
      } while (position > 0);
   }
}

Delegate Function Searcher(searchString As String, _
                           start As Integer,  _
                           count As Integer, _
                           type As StringComparison) As Integer

Module DelegateExample
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim position As Integer = 0
      Dim finder As Searcher = AddressOf title.IndexOf
      Do
         Dim characters As Integer = title.Length - position
         position = finder("the", position, characters, _
                         StringComparison.InvariantCultureIgnoreCase) 
         If position >= 0 Then
            position += 1
            Console.WriteLine("'The' found at position {0} in {1}.", _
                              position, title)
         End If   
      Loop While position > 0   
   End Sub
End Module

次の例では、 Func<T1,T2,T3,T4,TResult> 新しいデリゲートを明示的に定義し、名前付きメソッドを割り当てるのではなく、デリゲートをインスタンス化することによって、このコードを簡略化します。The following example simplifies this code by instantiating the Func<T1,T2,T3,T4,TResult> delegate instead of explicitly defining a new delegate and assigning a named method to it.

using System;

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Func<string, int, int, StringComparison, int> finder = title.IndexOf;
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters,
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.",
                              position, title);
         }
      } while (position > 0);
   }
}

Module DelegateExample
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim position As Integer = 0
      Dim finder As Func(Of String, Integer, Integer, StringComparison, Integer) _
                    = AddressOf title.IndexOf
      Do
         Dim characters As Integer = title.Length - position
         position = finder("the", position, characters, _
                         StringComparison.InvariantCultureIgnoreCase) 
         If position >= 0 Then
            position += 1
            Console.WriteLine("'The' found at position {0} in {1}.", _
                              position, title)
         End If   
      Loop While position > 0   
   End Sub
End Module

Func<T1,T2,T3,T4,TResult>次の例に示すように、C# では、匿名メソッドでデリゲートを使用できます。You can use the Func<T1,T2,T3,T4,TResult> delegate with anonymous methods in C#, as the following example illustrates. (匿名メソッドの概要については、「 匿名メソッド」を参照してください)。(For an introduction to anonymous methods, see Anonymous Methods.)

using System;

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Func<string, int, int, StringComparison, int> finder =
           delegate(string s, int pos, int chars, StringComparison type)
           { return title.IndexOf(s, pos, chars, type); };
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters,
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.",
                              position, title);
         }
      } while (position > 0);
   }
}

次の例に示すように、ラムダ式をデリゲートに割り当てることもでき Func<T1,T2,T3,T4,TResult> ます。You can also assign a lambda expression to a Func<T1,T2,T3,T4,TResult> delegate, as the following example illustrates. (ラムダ式の概要については、「 ラムダ式 」と「 ラムダ式」を参照してください)。(For an introduction to lambda expressions, see Lambda Expressions and Lambda Expressions.)

using System;

public class DelegateExample
{
   public static void Main()
   {
      string title = "The House of the Seven Gables";
      int position = 0;
      Func<string, int, int, StringComparison, int> finder =
           (s, pos, chars, type) => title.IndexOf(s, pos, chars, type);
      do
      {
         int characters = title.Length - position;
         position = finder("the", position, characters,
                         StringComparison.InvariantCultureIgnoreCase);
         if (position >= 0)
         {
            position++;
            Console.WriteLine("'The' found at position {0} in {1}.",
                              position, title);
         }
      } while (position > 0);
   }
}

Module DelegateExample
   Public Sub Main()
      Dim title As String = "The House of the Seven Gables"
      Dim position As Integer = 0
      Dim finder As Func(Of String, Integer, Integer, StringComparison, Integer) _
                    = Function(s, pos, chars, type) _
                    title.IndexOf(s, pos, chars, type)
      Do
         Dim characters As Integer = title.Length - position
         position = finder("the", position, characters, _
                         StringComparison.InvariantCultureIgnoreCase) 
         If position >= 0 Then
            position += 1
            Console.WriteLine("'The' found at position {0} in {1}.", _
                              position, title)
         End If   
      Loop While position > 0   
   End Sub
End Module

ラムダ式の基になる型は、汎用デリゲートの1つです Func 。The underlying type of a lambda expression is one of the generic Func delegates. これにより、ラムダ式をデリゲートに明示的に代入せずに、パラメーターとして渡すことができます。This makes it possible to pass a lambda expression as a parameter without explicitly assigning it to a delegate. 特に、名前空間の型の多くのメソッドに System.Linq パラメーターがあるため Func 、デリゲートを明示的にインスタンス化せずにこれらのメソッドをラムダ式に渡すことができ Func ます。In particular, because many methods of types in the System.Linq namespace have Func parameters, you can pass these methods a lambda expression without explicitly instantiating a Func delegate.

拡張メソッド

適用対象