Action<T1,T2> Action<T1,T2> Action<T1,T2> Action<T1,T2> Delegate

Definition

Kapselt eine Methode, die über zwei Parameter verfügt und keinen Wert zurückgibt.Encapsulates a method that has two parameters and does not return a value.

generic <typename T1, typename T2>
public delegate void Action(T1 arg1, T2 arg2);
public delegate void Action<in T1,in T2>(T1 arg1, T2 arg2);
type Action<'T1, 'T2> = delegate of 'T1 * 'T2 -> unit
Public Delegate Sub Action(Of In T1, In T2)(arg1 As T1, arg2 As T2)

Typparameter

T1

Der Typ des ersten Parameters der Methode, die dieser Delegat kapselt.The type of the first parameter of the method that this delegate encapsulates.

T2

Der Typ des zweiten Parameters der Methode, die dieser Delegat kapselt.The type of the second parameter of the method that this delegate encapsulates.

Parameter

arg1

Der erste Parameter der Methode, die dieser Delegat kapselt.The first parameter of the method that this delegate encapsulates.

arg2

Der zweite Parameter der Methode, die dieser Delegat kapselt.The second parameter of the method that this delegate encapsulates.

Vererbung
Action<T1,T2>Action<T1,T2>Action<T1,T2>Action<T1,T2>

Hinweise

Sie können die Action<T1,T2> Delegat, der eine Methode als Parameter übergeben werden, ohne explizit einen benutzerdefinierten Delegaten zu deklarieren.You can use the Action<T1,T2> delegate to pass a method as a parameter without explicitly declaring a custom delegate. Die der gekapselte Methode muss die Signatur der Methode entsprechen, die von diesem Delegaten definiert ist.The encapsulated method must correspond to the method signature that is defined by this delegate. Dies bedeutet, dass die gekapselte Methode müssen zwei Parameter, die beide an ihn als Wert übergeben werden, und sie müssen keinen Wert zurück.This means that the encapsulated method must have two parameters that are both passed to it by value, and it must not return a value. (In C# muss die Methode zurückgeben void.(In C#, the method must return void. In Visual Basic muss es vom definiert werden die Sub...End SubIn Visual Basic, it must be defined by the SubEnd Sub erstellen.construct. Sie können auch eine Methode, die einen Wert zurückgibt, der ignoriert wird sein.) In der Regel wird eine solche Methode zum Ausführen eines Vorgangs verwendet.It can also be a method that returns a value that is ignored.) Typically, such a method is used to perform an operation.

Hinweis

Um eine Methode zu verweisen, die über zwei Parameter verfügt und einen Wert zurückgibt, verwenden Sie den generischen Func<T1,T2,TResult> stattdessen delegieren.To reference a method that has two parameters and returns a value, use the generic Func<T1,T2,TResult> delegate instead.

Bei Verwendung der Action<T1,T2> Delegaten, Sie müssen nicht explizit einen Delegaten definieren, die eine Methode mit zwei Parametern kapselt.When you use the Action<T1,T2> delegate, you do not have to explicitly define a delegate that encapsulates a method with two parameters. Der folgende Code deklariert beispielsweise explizit einen Delegaten, der mit dem Namen ConcatStrings.For example, the following code explicitly declares a delegate named ConcatStrings. Anschließend werden die Delegatinstanz einen Verweis auf eine der beiden Methoden zugewiesen.It then assigns a reference to either of two methods to its delegate instance. Eine Methode werden zwei Zeichenfolgen in die Konsole geschrieben; die zweite zwei Zeichenfolgen in eine Datei geschrieben.One method writes two strings to the console; the second writes two strings to a file.

using System;
using System.IO;

delegate void ConcatStrings(string string1, string string2);

public class TestDelegate
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      ConcatStrings concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = WriteToFile;
      else
         concat = WriteToConsole;
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}
Imports System.IO

Delegate Sub ConcatStrings(string1 As String, string2 As String)

Module TestDelegate
   Public Sub Main()
      
      Dim message1 As String = "The first line of a message."
      Dim message2 As String = "The second line of a message."
      Dim concat As ConcatStrings
      
      If Environment.GetCommandLineArgs().Length > 1 Then
         concat = AddressOf WriteToFile
      Else
         concat = AddressOf WriteToConsole
      End If   
      concat(message1, message2)         
   End Sub
   
   Private Sub WriteToConsole(string1 As String, string2 As String)
      Console.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
   End Sub
   
   Private Sub WriteToFile(string1 As String, string2 As String)
      Dim writer As StreamWriter = Nothing  
      Try
         writer = New StreamWriter(Environment.GetCommandLineArgs(1), False)
         writer.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
      Catch
         Console.WriteLine("File write operation failed...")
      Finally
         If writer IsNot Nothing Then writer.Close
      End Try      
   End Sub
End Module

Im folgende Beispiel wird dieser Code vereinfacht, durch die Instanziierung der Action<T1,T2> Delegaten aufrufen, anstatt explizit definieren einen neuen Delegaten und eine benannte Methode zugewiesen wird.The following example simplifies this code by instantiating the Action<T1,T2> delegate instead of explicitly defining a new delegate and assigning a named method to it.

using System;
using System.IO;

public class TestAction2
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      Action<string, string> concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = WriteToFile;
      else
         concat = WriteToConsole;
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}
Imports System.IO

Module TestAction2
   Public Sub Main()
      
      Dim message1 As String = "The first line of a message."
      Dim message2 As String = "The second line of a message."
      Dim concat As Action(Of String, String)
      
      If Environment.GetCommandLineArgs().Length > 1 Then
         concat = AddressOf WriteToFile
      Else
         concat = AddressOf WriteToConsole
      End If   
      concat(message1, message2)         
   End Sub
   
   Private Sub WriteToConsole(string1 As String, string2 As String)
      Console.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
   End Sub
   
   Private Sub WriteToFile(string1 As String, string2 As String)
      Dim writer As StreamWriter = Nothing  
      Try
         writer = New StreamWriter(Environment.GetCommandLineArgs(1), False)
         writer.WriteLine("{0}{1}{2}", string1, vbCrLf, string2)
      Catch
         Console.WriteLine("File write operation failed...")
      Finally
         If writer IsNot Nothing Then writer.Close
      End Try      
   End Sub
End Module

Sie können auch die Action<T1,T2> delegieren mit anonymen Methoden in C# geschrieben, wie im folgende Beispiel veranschaulicht.You can also use the Action<T1,T2> delegate with anonymous methods in C#, as the following example illustrates. (Eine Einführung in anonyme Methoden, finden Sie unter anonyme Methoden.)(For an introduction to anonymous methods, see Anonymous Methods.)

using System;
using System.IO;

public class TestAnonymousMethod
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      Action<string, string> concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = delegate(string s1, string s2) { WriteToFile(s1, s2); };
      else
         concat = delegate(string s1, string s2) { WriteToConsole(s1, s2);} ;
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}

Sie können auch einen Lambda-Ausdruck zuweisen einer Action<T1,T2> Instanz delegieren, wie im folgende Beispiel veranschaulicht.You can also assign a lambda expression to an Action<T1,T2> delegate instance, as the following example illustrates. (Eine Einführung in Lambda-Ausdrücke, finden Sie unter Lambda-Ausdrücke.)(For an introduction to lambda expressions, see Lambda Expressions.)

using System;
using System.IO;

public class TestLambdaExpression
{
   public static void Main()
   {
      string message1 = "The first line of a message.";
      string message2 = "The second line of a message.";
      Action<string, string> concat;
      
      if (Environment.GetCommandLineArgs().Length > 1)
         concat = (s1, s2) => WriteToFile(s1, s2);
      else
         concat = (s1, s2) => WriteToConsole(s1, s2);
         
      concat(message1, message2);
   }
  
   private static void WriteToConsole(string string1, string string2)
   {
      Console.WriteLine("{0}\n{1}", string1, string2);            
   }

   private static void WriteToFile(string string1, string string2)
   {
      StreamWriter writer = null;  
      try
      {
         writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
         writer.WriteLine("{0}\n{1}", string1, string2);
      }
      catch
      {
         Console.WriteLine("File write operation failed...");
      }
      finally
      {
         if (writer != null) writer.Close();
      }      
   }
}
Imports System.IO

Public Module TestLambdaExpression

   Public Sub Main()
      Dim message1 As String = "The first line of a message."
      Dim message2 As String = "The second line of a message."
      Dim concat As Action(Of String, String)
      
      If Environment.GetCommandLineArgs().Length > 1 Then
         concat = Sub(s1, s2) WriteToFile(s1, s2)
      Else
         concat = Sub(s1, s2) WriteToConsole(s1, s2)
      End If
         
      concat(message1, message2)
   End Sub
  
   Private Function WriteToConsole(string1 As String, string2 As String) As Integer
      Dim message As String = String.Format("{0}{1}{2}", string1, vbCrLf, string2)
      Console.WriteLine(message)
      Return message.Length
   End Function

   Private Function WriteToFile(string1 As String, string2 As String) As Integer
      Dim writer As StreamWriter = Nothing  
      Dim message As String = String.Format("{0}{1}{2}", string1, vbCrLf, string2)
      Dim charsWritten As Integer
      Try
         writer = New StreamWriter(Environment.GetCommandLineArgs()(1), False)
         writer.WriteLine(message)
      Catch
         Console.WriteLine("File write operation failed...")
      Finally
         If writer IsNot Nothing Then 
            writer.Close()
            charsWritten = message.Length
         Else
            charsWritten = 0
         End If
      End Try      
      Return charsWritten
   End Function
End Module

Extension Methods

GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate)

Ruft ein Objekt ab, das die Methode darstellt, die vom angegebenen Delegaten dargestellt wird.Gets an object that represents the method represented by the specified delegate.

Gilt für:

Siehe auch