Question

To keep myself interested, I try to put little Easter Eggs in my projects (mostly to amuse myself). I’ve seen some websites where you can type a series of letters “aswzaswz” and you get a “secret function” – how would I achieve this in C#?

I’ve assigned a “secret function” in the past by using modifier keys

        bool showFunThing = (Control.ModifierKeys & Keys.Control) == Keys.Control;

but wanted to get a bit more secretive (without the modifier keys) I just wanted the form to detect a certain word typed without any input … I’ve built a method that I think should do it:

    private StringBuilder _pressedKeys = new StringBuilder();

    protected override void OnKeyDown(KeyEventArgs e)
    {
        const string kWord = "fun";
        char letter = (char)e.KeyValue;
        if (!char.IsLetterOrDigit(letter))
        { return; }
        _pressedKeys.Append(letter);
        if (_pressedKeys.Length == kWord.Length)
        {
            if (_pressedKeys.ToString().ToLower() == kWord)
            {
                MessageBox.Show("Fun");
                _pressedKeys.Clear();
            }
        }
        base.OnKeyDown(e);
    }

Now I need to wire it up but I can’t figure out how I’m supposed to raise the event in the form designer … I’ve tried this:

    this.KeyDown +=new System.Windows.Forms.KeyEventHandler(OnKeyDown);

and a couple of variations on this but I’m missing something because it won’t fire (or compile). It tells me that the OnKeyDown method is expecting a certain signature but I’ve got other methods like this where I haven’t specified arguments.

I fear that I may have got myself confused so I am turning to SO for help … anyone?

EDIT: The ProcessCmdKey seems to be the way that works with the following:

    private StringBuilder _pressedKeys = new StringBuilder();
    protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
    {
        const string kWord = "fun";
        char letter = (char)keyData;
        if (!char.IsLetterOrDigit(letter))
        {return true;}
        _pressedKeys.Append(letter);
        if (_pressedKeys.Length == kWord.Length)
        {
         if (_pressedKeys.ToString().ToLower() == kWord)
            {
                MessageBox.Show("Fun");
                _pressedKeys.Clear();
            }
            _pressedKeys.Clear();
        }
     return true;
    }

Thanks all!

Answer 1

Try this:

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
    if (keyData == (Keys.P|Keys.Control))
    {
        //do my prank
        return true;
    }
    return base.ProcessCmdKey(ref msg, keyData);
}

This will fire when you press CTRL + P.

refer: ProcessCmdKey

This method is called during message preprocessing to handle command
keys. Command keys are keys that always take precedence over regular
input keys. Examples of command keys include accelerators and menu
shortcuts. The method must return true to indicate that it has
processed the command key