How can I detect Ctrl-Alt-Del either before or after the OS detects it?

I need to initialize a variable when the user presses Ctrl-Alt-Del. Because this key combination is treated differently than others, the Windows Security Dialog Box appears immediately after it is pressed and my program can not detect whether it is pressed.

I tried adding the code below to the KeyDown event, but it does not work.

     if ( (Keyboard.Modifiers == (ModifierKeys.Control开发者_C百科 | ModifierKeys.Alt)) && Keyboard.IsKeyDown(Key.Delete))
     {
         // Initialize a variable
     }

If it is possible, how can I detect this key combination before the OS detects it? If not, how can I detect it after the OS?

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In short, you can't.

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Even if you can, you should not, as changing the meaning of Ctrl-Alt-Del would confuse users.

I hope it is not possible to-do without replacing keyboard drivers etc, as otherwise an application could make it impossible for the user to get to the task manager to kill the application.