Action Action Action Action Delegate

定義

封裝沒有參數且沒有傳回值的方法。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()
繼承

備註

您可以使用這個委派, 將方法當做參數傳遞, 而不需要明確宣告自訂委派。You can use this delegate to pass a method as a parameter without explicitly declaring a custom delegate. 封裝的方法必須對應到此委派所定義的方法簽章。The encapsulated method must correspond to the method signature that is defined by this delegate. 這表示封裝的方法不能有任何參數, 而且沒有傳回值。This means that the encapsulated method must have no parameters and no return value. (在C#中, 方法必須void傳回。(In C#, the method must return void. 在 Visual Basic 中, 它必須由Sub...End SubIn Visual Basic, it must be defined by the SubEnd Sub 建構.construct. 它也可以是傳回已忽略值的方法)。一般來說, 這種方法是用來執行作業。It can also be a method that returns a value that is ignored.) Typically, such a method is used to perform an operation.

注意

若要參考沒有任何參數並傳回值的方法, 請改用泛型Func<TResult>委派。To reference a method that has no parameters and returns a value, use the generic Func<TResult> delegate instead.

當您使用Action委派時, 您不需要明確定義封裝無參數程式的委派。When you use the Action delegate, you do not have to explicitly define a delegate that encapsulates a parameterless procedure. 例如, 下列程式碼會明確宣告名ShowValue為的委派, 並將Name.DisplayToWindow實例方法的參考指派給其委派實例。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

下列範例會藉由具現化Action委派來簡化此程式碼, 而不是明確定義新的委派, 並將命名的方法指派給它。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

您也可以在中Action C#使用具有匿名方法的委派, 如下列範例所示。You can also use the Action delegate with anonymous methods in C#, as the following example illustrates. (如需匿名方法的簡介, 請參閱匿名方法)。(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();
   }
}

您也可以將 lambda 運算式指派給Action委派實例, 如下列範例所示。You can also assign a lambda expression to an Action delegate instance, as the following example illustrates. (如需 lambda 運算式的簡介, 請參閱Lambda 運算式)。(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

擴充方法

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

取得表示特定委派所代表之方法的物件。Gets an object that represents the method represented by the specified delegate.

適用於

另請參閱