How Can I make the event of Activate Windows to run only one time?

In order to make the event of Activate Windows to run only one time, I write the code below

this.Activated-=new System.EventHandler(this.Form1_Activated);

Is it correct but It certain can work well. but it seems it is not a good code.

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace WindowsApplication1
{

public class Form1 : System.Windows.Forms.Form
{

private System.ComponentModel.Container components = null;

public Form1()
{

InitializeComponent();

}

  protected override void Dispose( bool disposing )
  {
   if( disposing )
   {
    if (components != null)
    {
     components.Dispose();
    }
   }
   base.Dispose( disposing );
  }

#region Windows

private void InitializeComponent()
{

   this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
   this.ClientSize = new System.Drawing.Size(292, 266);
   this.Name = "Form1";
   this.Text = "Form1";
   this.Activated += new System.EventHandler(this.Form1_Activated);

}
#endregion

  [STAThread]
  static void Main()
  {
   Application.Run(new Form1());
  }

  private void Form1_Activated(object sender, System.EventArgs e)
  {
   this.Activated-=new System.EventHandler(this.Form1_Activated);
  }
}
}

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How Can I make the event of Activate Windows to run only one time?

jjmcguire

The code is certainly correct.

I find it better to override the method that actually raises the event, instead of attaching to it. However this is typically a personal preference.

For example:

public class Form1 : Form
{
   ...
   private bool _FirstActivate = true;

   protected override OnActivated(EventArgs e)
   {
      if (_FirstActivate)
      {
         _FirstActivate = false;
         ...
      }

      base.OnActivated(e);
   }
}

Ant999

Have you tested it My initial reaction was that this can't work.

this.Activated-=new System.EventHandler(this.Form1_Activated);

here you are removing a NEW event handler for the method, not the one allready added.

private void Form1_Activated(object sender, EventArgs e)

{

this.Activated -= activEventHandler;

}

//these two items is to be put in the designer in whidbey
private System.EventHandler activEventHandler;

this.Activated += (activEventHandler = new System.EventHandler(this.Form1_Activated));

sinankoylu
No the code is correct.

You don't need to have the same instance of the delegate (or event handler) to unhook a method from an event.
Zigzag
RE. here you are removing a NEW event handler for the method, not the one allready added.

Yes, I have test the code, it work well. but I agree with your point, I don't know why it can work well, so I don't think it's a good code!

"here you are removing a NEW event handler for the method, not the one allready added. " I agree with it. I don't know why it can work, could you tell me
Mike Bravo
Hi,

There is nothing wrong with it. It's the correct way to unregister an Eventhna in C#. If your application requires that the event not be fired again, then you can unregister it the way you have done it.

Regards,
Vikram
How Can I make the event of Activate Windows to run only one time?

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How Can I make the event of Activate Windows to run only one time?

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Windows Forms

How Can I make the event of Activate Windows to run only one time?

How Can I make the event of Activate Windows to run only one time?

jjmcguire

Ant999

sinankoylu

Zigzag

Mike Bravo