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

Definizione

Incapsula un metodo che presenta due parametri e non restituisce alcun valore.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)

Parametri di tipo

T1

Tipo del primo parametro del metodo incapsulato da questo delegato.The type of the first parameter of the method that this delegate encapsulates.

T2

Tipo del secondo parametro del metodo incapsulato da questo delegato.The type of the second parameter of the method that this delegate encapsulates.

Parametri

arg1

Primo parametro del metodo incapsulato da questo delegato.The first parameter of the method that this delegate encapsulates.

arg2

Secondo parametro del metodo incapsulato da questo delegato.The second parameter of the method that this delegate encapsulates.

Ereditarietà
Action<T1,T2>Action<T1,T2>Action<T1,T2>Action<T1,T2>

Commenti

È possibile usare il Action<T1,T2> delegato passa un metodo come parametro senza dichiarare in modo esplicito un delegato personalizzato.You can use the Action<T1,T2> delegate to pass a method as a parameter without explicitly declaring a custom delegate. Metodo incapsulato deve corrispondere alla firma del metodo che è definita da questo delegato.The encapsulated method must correspond to the method signature that is defined by this delegate. Ciò significa che il metodo incapsulato deve avere due parametri che sono entrambi passati al metodo tramite valore e non deve essere restituito un valore.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#, il metodo deve restituire void.(In C#, the method must return void. In Visual Basic deve essere definito per il Sub...End SubIn Visual Basic, it must be defined by the SubEnd Sub costrutto.construct. Può anche essere un metodo che restituisce un valore che viene ignorato.) In genere, tale metodo viene utilizzato per eseguire un'operazione.It can also be a method that returns a value that is ignored.) Typically, such a method is used to perform an operation.

Nota

Per fare riferimento a un metodo che presenta due parametri e restituisce un valore, usare il tipo generico Func<T1,T2,TResult> delegato.To reference a method that has two parameters and returns a value, use the generic Func<T1,T2,TResult> delegate instead.

Quando si usa il Action<T1,T2> delegato, non è necessario definire in modo esplicito un delegato che incapsula un metodo con due parametri.When you use the Action<T1,T2> delegate, you do not have to explicitly define a delegate that encapsulates a method with two parameters. Ad esempio, il codice seguente dichiara in modo esplicito un delegato denominato ConcatStrings.For example, the following code explicitly declares a delegate named ConcatStrings. Assegna un riferimento a uno dei due metodi all'istanza di delegato.It then assigns a reference to either of two methods to its delegate instance. Un metodo scrive nella console; due stringhe il secondo scrive due stringhe in un file.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

Nell'esempio seguente viene semplificato il codice creando il Action<T1,T2> delegato anziché la definizione di un nuovo delegato e assegnarle un metodo denominato in modo esplicito.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

È anche possibile usare il Action<T1,T2> delegare con i metodi anonimi nel linguaggio c#, come illustrato nell'esempio seguente.You can also use the Action<T1,T2> delegate with anonymous methods in C#, as the following example illustrates. (Per un'introduzione ai metodi anonimi, vedere metodi anonimi.)(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();
      }      
   }
}

È anche possibile assegnare un'espressione lambda a un Action<T1,T2> delegare l'istanza, come illustrato nell'esempio seguente.You can also assign a lambda expression to an Action<T1,T2> delegate instance, as the following example illustrates. (Per un'introduzione alle espressioni lambda, vedere espressioni Lambda.)(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)

Ottiene un oggetto che rappresenta il metodo rappresentato dal delegato specificato.Gets an object that represents the method represented by the specified delegate.

Si applica a

Vedi anche