5

I want that the form will not close by doing Alt + F4 but if Application.Exit() or this.Close is called from the same Form, it should be closed.

I tried CloseReason.UserClosing but still no help.

Cœur
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Rick2047
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4 Answers4

20

If you need to filter out Alt + F4 event only (leaving clicking of close box, this.Close() and Application.Exit() to behave as usual) then I can suggest the following:

  1. Set form's KeyPreview property to true;

  2. Wire up form's FormClosing and KeyDown events:

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
    if (_altF4Pressed)
    {
        if (e.CloseReason == CloseReason.UserClosing)
            e.Cancel = true;
        _altF4Pressed = false;
    }
}

private bool _altF4Pressed;
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Alt && e.KeyCode == Keys.F4)
        _altF4Pressed = true;
}
Wai Ha Lee
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Regent
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2

It's very easy you can do it by set SuppressKeyPress property to true on Form_Keydown EventHandler as below.

        if (e.KeyCode == Keys.F4 && e.Alt)
        {
            e.SuppressKeyPress = true;

        }

With this you can also close your active form by set SuppressKeyPress Property to false on same eventHandller or any other way.

mahesh
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0

Capture Alt+F4 hotkey by setting Form's KeyPreview property to true and overriding OnProcessCmdKey method.

Axarydax
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0

How did you use CloseReason?

See the sample code here: http://msdn.microsoft.com/en-us/library/system.windows.forms.form.formclosing.aspx

You need to set the Cancel property of the passed FormClosingEventArgs object to stop the form closing.

Mesh
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  • The problem with `FormClosing` event is that Alt+F4 and calling `this.Close()` won't be distinguishable -- they both will have `CloseReason.UserClosing`. – Regent Apr 15 '10 at 08:54
  • prior to calling this.Close() set a property that can be examined in FormClosing... – Mesh Apr 15 '10 at 08:59
  • this will work it you can actually control where to call form's `Close` method. What if it could be called by some third-party component at some moment?.. Also, `CloseReason.UserClosing` will be set when clicking form's close box. (It is desired behaviour?) – Regent Apr 15 '10 at 09:06