Action Action Action Action Delegate

Definizione

Incapsula un metodo che non presenta parametri e non restituisce alcun valore.Encapsulates a method that has no parameters and does not return a value.

public delegate void Action();
public delegate void Action();
type Action = delegate of unit -> unit
Public Delegate Sub Action()
Ereditarietà

Commenti

È possibile utilizzare questo delegato per passare un metodo come parametro senza dichiarare in modo esplicito un delegato personalizzato.You can use this delegate to pass a method as a parameter without explicitly declaring a custom delegate. Il metodo incapsulato deve corrispondere alla firma del metodo definita da questo delegato.The encapsulated method must correspond to the method signature that is defined by this delegate. Questo significa che il metodo incapsulato non deve avere parametri e nessun valore restituito.This means that the encapsulated method must have no parameters and no return value. In C#il metodo deve restituire void.(In C#, the method must return void. In Visual Basic, deve essere definito da Sub...End SubIn Visual Basic, it must be defined by the SubEnd Sub costruire.construct. Può anche essere un metodo che restituisce un valore ignorato. Questo metodo viene in genere usato 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 non presenta parametri e restituisce un valore, usare Func<TResult> invece il delegato generico.To reference a method that has no parameters and returns a value, use the generic Func<TResult> delegate instead.

Quando si usa il Action delegato, non è necessario definire in modo esplicito un delegato che incapsula una procedura senza parametri.When you use the Action delegate, you do not have to explicitly define a delegate that encapsulates a parameterless procedure. Il codice seguente, ad esempio, dichiara in modo esplicito un ShowValue delegato denominato e assegna un riferimento al Name.DisplayToWindow metodo di istanza all'istanza del delegato.For example, the following code explicitly declares a delegate named ShowValue and assigns a reference to the Name.DisplayToWindow instance method to its delegate instance.

using namespace System;
using namespace System::Windows::Forms;

public delegate void ShowValue();


public ref class Name
{
private:
   String^ instanceName;

public:
   Name(String^ name) 
   {
      instanceName = name;
   }

   void DisplayToConsole()
   {
      Console::WriteLine(this->instanceName);
   }

   void DisplayToWindow()
   {
      MessageBox::Show(this->instanceName);
   }
};

int main()
{
   Name^ testName = gcnew Name(L"Koani");
   ShowValue^ showMethod;
   showMethod = gcnew ShowValue(testName, &Name::DisplayToWindow);
   showMethod();
   return 0;
}
using System;
using System.Windows.Forms;

public delegate void ShowValue();

public class Name
{
   private string instanceName;
   
   public Name(string name)
   {
      this.instanceName = name;
   }

   public void DisplayToConsole()
   {
      Console.WriteLine(this.instanceName);
   }

   public void DisplayToWindow()
   {
      MessageBox.Show(this.instanceName);
   }
}

public class testTestDelegate
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      ShowValue showMethod = testName.DisplayToWindow;
      showMethod();
   }
}
Public Delegate Sub ShowValue

Public Class Name
   Private instanceName As String
   
   Public Sub New(name As String)
      Me.instanceName = name
   End Sub
   
   Public Sub DisplayToConsole()
      Console.WriteLine(Me.instanceName)
   End Sub   
   
   Public Sub DisplayToWindow()
      MsgBox(Me.instanceName)
   End Sub   
End Class

Public Module testDelegate
   Public Sub Main()
      Dim testName As New Name("Koani")
      Dim showMethod As ShowValue = AddressOf testName.DisplayToWindow
      showMethod   
   End Sub
End Module

Nell'esempio seguente viene semplificato questo codice creando un'istanza Action del delegato anziché definendo in modo esplicito un nuovo delegato e assegnando un metodo denominato.The following example simplifies this code by instantiating the Action delegate instead of explicitly defining a new delegate and assigning a named method to it.

#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Windows::Forms;

public ref class Name
{
private:
   String^ instanceName;
   
public:
   Name(String^ name)
   {
      instanceName = name;
   }

   void DisplayToConsole()
   {
      Console::WriteLine(this->instanceName);
   }

   void DisplayToWindow()
   {
      MessageBox::Show(this->instanceName);
   }
};


int main()
{
   Name^ testName = gcnew Name(L"Koani");
   System::Action^ showMethod;
   showMethod += gcnew Action(testName, &Name::DisplayToWindow);
   showMethod();
   return 0;
}
using System;
using System.Windows.Forms;

public class Name
{
   private string instanceName;
   
   public Name(string name)
   {
      this.instanceName = name;
   }

   public void DisplayToConsole()
   {
      Console.WriteLine(this.instanceName);
   }

   public void DisplayToWindow()
   {
      MessageBox.Show(this.instanceName);
   }
}

public class testTestDelegate
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      Action showMethod = testName.DisplayToWindow;
      showMethod();
   }
}
Public Class Name
   Private instanceName As String
   
   Public Sub New(name As String)
      Me.instanceName = name
   End Sub
   
   Public Sub DisplayToConsole()
      Console.WriteLine(Me.instanceName)
   End Sub   
   
   Public Sub DisplayToWindow()
      MsgBox(Me.instanceName)
   End Sub   
End Class

Public Module testDelegate
   Public Sub Main()
      Dim testName As New Name("Koani")
      Dim showMethod As Action = AddressOf testName.DisplayToWindow
      showMethod   
   End Sub
End Module

È anche possibile usare il Action delegato con i metodi anonimi in C#, come illustrato nell'esempio seguente.You can also use the Action 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.Windows.Forms;

public class Name
{
   private string instanceName;
   
   public Name(string name)
   {
      this.instanceName = name;
   }

   public void DisplayToConsole()
   {
      Console.WriteLine(this.instanceName);
   }

   public void DisplayToWindow()
   {
      MessageBox.Show(this.instanceName);
   }
}

public class Anonymous
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      Action showMethod = delegate() { testName.DisplayToWindow();} ;
      showMethod();
   }
}

È anche possibile assegnare un'espressione lambda a un' Action istanza di delegato, come illustrato nell'esempio seguente.You can also assign a lambda expression to an Action 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.Windows.Forms;

public class Name
{
   private string instanceName;
   
   public Name(string name)
   {
      this.instanceName = name;
   }

   public void DisplayToConsole()
   {
      Console.WriteLine(this.instanceName);
   }

   public void DisplayToWindow()
   {
      MessageBox.Show(this.instanceName);
   }
}

public class LambdaExpression
{
   public static void Main()
   {
      Name testName = new Name("Koani");
      Action showMethod = () => testName.DisplayToWindow();
      showMethod();
   }
}
Public Class Name
   Private instanceName As String
   
   Public Sub New(name As String)
      Me.instanceName = name
   End Sub
   
   Public Function DisplayToConsole() As Integer
      Console.WriteLine(Me.instanceName)
      Return 0
   End Function
   
   Public Function DisplayToWindow() As Integer
      Return MsgBox(Me.instanceName)
   End Function      
End Class

Module LambdaExpression
   Public Sub Main()
      Dim name1 As New Name("Koani")
      Dim methodCall As Action = Sub() name1.DisplayToWindow()
      methodCall()
   End Sub
End Module

Metodi di estensione

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