Disable Alt + F4, but allow code to close the form, CloseReason.UserClosing does not help

Question

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

I tried CloseReason.UserClosingbut still didn't help.

Answer 1

If you need to filter out the Alt+ event F4(leaving the click on the close button this.Close()and Application.Exit()behaving as usual), I can suggest the following:

• Set the form KeyPreview property true;

• Connect form FormClosingand KeyDownevents:

  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;
  }
  

Answer 2

, , SuppressKeyPress true Form_Keydown EventHandler, .

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

        }

, SuppressKeyPress false eventHandller .

Answer 3

Capture Alt + F4, Form KeyPreview true overriding OnProcessCmdKey.

Answer 4

CloseReason?

. : http://msdn.microsoft.com/en-us/library/system.windows.forms.form.formclosing.aspx

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