デリゲートとイベント

COBOL のデリゲートとイベント

      $set sourceformat(free)
      $set ilusing "System"
delegate-id MsgArrivedEventHandler.
procedure division using by value messag as string.
end delegate.

class-id a.

    01 MsgArrivedEvent type "MsgArrivedEventHandler" event static.

    *> Delegates must be used with events in COBOL
    method-id main static.
        set MsgArrivedEvent to type Delegate::Combine
        (
            MsgArrivedEvent,
            new MsgArrivedEventHandler(self::My_MsgArrivedEventCallback)
        ) as type MsgArrivedEventHandler

        *> Throws exception if obj is null
        invoke MsgArrivedEvent::Invoke("Test message")

        set MsgArrivedEvent to type Delegate::Remove
        (
            MsgArrivedEvent,
            new MsgArrivedEventHandler(self::My_MsgArrivedEventCallback)
        ) as type MsgArrivedEventHandler

      invoke self::add_MsgArrivedEvent
       (new MsgArrivedEventHandler(self::My_MsgArrivedEventCallback))
       invoke MsgArrivedEvent::Invoke("Test message 2")
    end method main.

    method-id My_MsgArrivedEventCallback static.
       procedure division using by value str as string.
       display str
    end method.
end class a. 

C# のデリゲートとイベント

delegate void MsgArrivedEventHandler(string message);

event MsgArrivedEventHandler MsgArrivedEvent;







// Delegates must be used with events in C#


MsgArrivedEvent +=
    new MsgArrivedEventHandler(My_MsgArrivedEventCallback);
// Throws exception if obj is null
MsgArrivedEvent("Test message");
MsgArrivedEvent -=
    new MsgArrivedEventHandler(My_MsgArrivedEventCallback);



using System.Windows.Forms;

Button MyButton = new Button();
MyButton.Click += new System.EventHandler(MyButton_Click);

private void MyButton_Click(object sender, System.EventArgs e)
{
  MessageBox.Show(this, "Button was clicked", "Info",
    MessageBoxButtons.OK, MessageBoxIcon.Information);
}

VB.NET のデリゲートとイベント

Delegate Sub MsgArrivedEventHandler(ByVal message As String)

Event MsgArrivedEvent As MsgArrivedEventHandler







' or to define an event which declares a delegate implicitly
Event MsgArrivedEvent(ByVal message As String)

AddHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback
' Won't throw an exception if obj is Nothing
RaiseEvent MsgArrivedEvent("Test message")
RemoveHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback
Imports System.Windows.Forms

Dim WithEvents MyButton As Button   ' WithEvents can't be used on local variable
MyButton = New Button

Private Sub MyButton_Click(ByVal sender As System.Object, _
  ByVal e As System.EventArgs) Handles MyButton.Click
  MessageBox.Show(Me, "Button was clicked", "Info", _
    MessageBoxButtons.OK, MessageBoxIcon.Information)
End Sub

これらの例の一部は、ハーディング大学コンピューター サイエンス学部の Frank McCown 博士が作成したもので、クリエイティブ コモンズ ライセンスに基づいて使用が許可されています。