Triple Mouse Click in C#?

Have a look at this: Mousebuttoneventargs.clickcount

That should cover it I suppose.

DO THIS:

    private int _clicks = 0;
    private System.Windows.Forms.Timer _timer = new System.Windows.Forms.Timer();
    private void txtTextMessage_MouseUp(object sender, MouseEventArgs e)
    {
        _timer.Stop();
        _clicks++;
        if (_clicks == 3)
        {
            // this means the trip click happened - do something
            txtTextMessage.SelectAll();
            _clicks = 0;
        }
        if (_clicks < 3)
        {
            _timer.Interval = 500;
            _timer.Start();
            _timer.Tick += (s, t) =>
            {
                _timer.Stop();
                _clicks = 0;
            };
        }
    }

You just have to store the time when a double click occured in that Box. Then, in the handler for the single click, check if a double click happened not more than N milliseconds ago (N = 300 or so).

In this case, call your TripleClick() function directly or define a new event for you derived "TripleClickAwareTextBox".