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Creating Event Handlers at Run Time for Windows Forms

Visual Studio .NET 2003

In addition to creating events using the Windows Forms Designer, you can also create an event handler at run time. This action allows you to connect event handlers based on conditions in code at run time as opposed to having them connected when the program initially starts.

To create an event handler at run time

  1. Open the form in the Code Editor that you want to add an event handler to.
  2. Add a method to your form with the method signature for the event that you want to handle.

    For example, if you were handling the Click event of a Button control, you would create a method such as the following:

    ' Visual Basic
    Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
       ' Add event handler code here.
    End Sub
    
    // C#
    private void button1_Click(object sender, System.EventArgs e) 
    {
    // Add event handler code here.
    }
    
    // C++
    private:
       System::Void button1_Click(System::Object *  sender, 
          System::EventArgs *  e)
       {
          // Add event handler code here.
       }
    
  3. Add code to the event handler as appropriate to your application.
  4. Determine which form or control you want to create an event handler for.
  5. In a method within your form's class, add code that specifies the event handler to handle the event. For example, the following code specifies the event handler button1_Click handles the Click event of a Button control:
    ' Visual Basic
    AddHandler Button1.Click, AddressOf Button1_Click 
    
    // C#
    button1.Click += new EventHandler(button1_Click);
    
    // C++
    button1->add_Click(new System::EventHandler(this, button1_Click));
    

    The AddHandler method demonstrated in the Visual Basic code above establishes a click event handler for the button.

See Also

Event Handling in Windows Forms | Introduction to Event Handlers in Windows Forms | Creating Windows Forms | Troubleshooting Inherited Event Handlers in Visual Basic .NET

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