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key press to form only; not child controls

Posted on 2004-04-03
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Last Modified: 2007-12-19
I have a form with child controls.  When the form opens, one of the child controls (a radio button) gets focus.  Then when I press the up/down arrow keys, a radio button group selection changes.

What I want is for the form to always get the key press events and I dont ever want the child controls to get a key press event.  I tried over-riding the OnKeyDown method, but since a child control on the form has focus, it gets the key press event and not the parent form.  

How can I cause the parent form to get all key press events and stop them from being propigated to the child controls?  The user still needs to interact with the controls (sliders, radio button, etc), but even if a slider has focus, if the user presses a key, I want the parent form to get this event and cosume it and not let the slider get it.

thanks
Bryan
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Question by:bryanwells
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8 Comments
 
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Expert Comment

by:Éric Moreau
ID: 10747972
Have you tried setting the Form's KeyPreview property to True? With this event Form's KeyDown, KeyUp, and KeyPress events will be raised BEFORE those of the controls.

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LVL 70

Expert Comment

by:Éric Moreau
ID: 10747974
Sorry, forget my comment. I thought I was into the VB topic!
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Expert Comment

by:Éric Moreau
ID: 10747991
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Expert Comment

by:RichardCleaver
ID: 10748512
Try setting Form.KeyPreview to true.  Then in the keyboard event set e.Handled = true.  This will stop any controls from receiving the input.

For example:

private void FormX_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e) {
      if (e.Alt && e.KeyCode == Keys.F4 || e.KeyCode == Keys.Escape) {
      // Do some processing if the Escape key or Alt+F4 is pressed.  i.e. FormX.Close()
      e.Handled = true;
      }
}
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Author Comment

by:bryanwells
ID: 10749352
This almost works.  But my radio buttons come up selected first, and the arrow keys still toggle the radio buttons without getting a call to my key down event handler in my form.  Once I put focus on another control, it works as expected.  Is there something special about radio buttons and up/down arrow keys?
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Expert Comment

by:RichardCleaver
ID: 10749724
Radio buttons always act as a group in a container.  The container in this case is the form.

Try putting 'this.ActiveControl = MyControl' in your FormX_Load event.  This should put the focus on another control (MyControl) before the form is visible.
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Author Comment

by:bryanwells
ID: 10749752
This is very close to what I want.  I just wish I could stop the arrow keys from toggling the radio buttons.  I have them in a group box instead of in the form directly, but still it is the same behavior as you described.  How can I  disable radio buttons from responding to the up/down arrow keys?
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Accepted Solution

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caner_elci earned 125 total points
ID: 10796385
You can add a message filter to your application and listen for WM_KEYDOWN and WM_KEYUP messages there. PreFilterMessage method of IMessageFilter is what you need.

Check out IMessageFilter and Application.AddMessageFilter() for further information.

Also you can try setting TabStop property to false for your radio buttons...

Caner ELCI
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