Question

Can I put a thread on a mouse event handler?

Calls_Calls.MouseUp += new MouseEventHandler(Calls_Calls_MouseUp);

How to add a thread over this?

Answer 1

I would set up the event handler in the same way, but in the Calls_Calls_MouseUp method you can launch a thread to do the work:

private void Calls_Calls_MouseUp(object sender, MouseEventArgs e)
{
    ThreadPool.QueueUserWorkItem(state => {
       // do the work here
    });
}

However, I typically try to have my event handlers as unaware as possible, just calling some other method, often based on some condition:

private void Calls_Calls_MouseUp(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        DoSomething();
    }
}

private void DoSomething()
{
    ThreadPool.QueueUserWorkItem(state => {
       // do the work here
    });
}

This gives you the ability to trigger the exact same behavior from something else than the MouseUp event on a certain control (so that you can have the same behavior on a menu item, a toolbar button and perhaps a regular command button). It may also open up the possibility to have unit tests on the functionality (even though that is somewhat trickier with asynchronous code).