WinForms - action after resize event

Question

Is it possible to perform a specific action after the resize event (of the user control), for example when mouse button is released? I need to manually resize an inner control and doing it on every single firing of the event would be quite, hmm, inefficient...

Solution 1

Just use the ResizeEnd event:

private void Form1_ResizeEnd(object sender, EventArgs e)
{
   // Your code here
}

From MSDN:

The ResizeEnd event is raised when the user finishes resizing a form, typically by dragging one of the borders or the sizing grip located on the lower-right corner of the form, and then releasing it. For more information about the resizing operation.

Solution 2

You can fake a local ResizeEnd like this:

public class Dummy:UserControl
{

    private readonly Timer _tDelayedResize;

    public Dummy()
    {
        this.Resize += this_Resize;
        _tDelayedResize = new Timer();
        _tDelayedResize.Interval = 5;
        _tDelayedResize.Tick += this_ResizeEnd;
    }

    void this_Resize(object sender, EventArgs e)
    {
        _tDelayedResize.Stop();
        _tDelayedResize.Start();
    }

    void this_ResizeEnd(object sender, EventArgs e)
    {
        _tDelayedResize.Stop();

        //Do your ResizeEnd logic here
        //...
    }

}

The interval can be modified. The higher it is the more delay after the last resize event it will be.

Solution 3

Another option if you are using a control and not a form and would like to perform actions after the resize has been completed (user stopped resizing control):

private int resizeTimeout = 0;
private Task resizeTask;

public void OnResize()
{
  resizeTimeout = 300; //Reset timeout
  //Only resize on completion. This after resizeTimeout if no interaction.
  if (resizeTask == null || resizeTask.IsCompleted)
  {
    resizeTask = Task.Run(async () =>
    {
      //Sleep until timeout has been reached
      while (resizeTimeout > 0)
      {
        await Task.Delay(100);
        resizeTimeout -= 100;
      }
      ResizeControl();
    });
  }
}

private void ResizeControl()
{
  if (this.InvokeRequired)
  {
    //Call the same method in the context of the main UI thread.
    this.Invoke((MethodInvoker)delegate { ResizeControl(); });
  }
  else
  {
    // Do resize actions here
  }
}

Comments

[djdd87]

@leppie - the Resize happens a number of times during a user resizing a window. He wants an event that occurs when the user has finished resizing.

[brovar]

Very tempting and I'd probably have already used it, but it's happening in the user control (I forgot to specify that, sorry) and I don't have access to the form's events.

[leppie]

@brovar: That's baloney! Every control has a ParentForm property. So in fact you have all that accessible!

[djdd87]

@Why can you not just add a ResizeMeNow() method to the user control and call it on the Form's ResizeEnd event?

[djdd87]

@brovar - or like leppie has said, you can just hook into UserControl.ParentForm.ResizeEnd+= ... etc.

[brovar]

Yes, I do have ParentForm, but it's not accessible after Handles and AddHandler is not something very welcomed in this application's code. (yep, VB.NET, not c#)

[brovar]

Just like Resize, time after time.

[Jazimov]

I'm just looking at this code (I didn't run it)--but it seems to me that this will equate to a Resizing event and not a ResizeEnd event.

[brovar]

I don't even remember what the question was actually about, but wow! Thanks for answering!