Question

I want to subscribe and unsubscribe from a ToolStripButton‘s Click event using a globally declared delegate as discribed in this SO question and subsequent answers. I have the following delegate declared globally in my class

private delegate void StopTask(ref MainForm _mainForm, 
    Task _task, CancellationTokenSource _cancelSource);

I then set this delegate to hold a method as follows

StopTask cancelTask = UtilsTPL.CancelRunningProcess;

where in the public class UtilsTPL, CancelRunningProcess is defined as

public static void CancelRunningProcess(ref MainForm _mainForm, Task _task, 
    CancellationTokenSource _cancelSource)
{
    // Some really amazing code...
}

I then try to add the delegate to my ToolStripButton click event like this (and also unsubscribe as shown)

mainForm.stopButton.Click += cancelTask;
mainForm.stopButton.Click -= cancelTask;

This clearly does not work, as there is a glaring type miss-match.

How do I subscribe/unsubscribe the consistant delegate cancelTask to the buttons click event? Thanks for your time.

Note: I am doing this so that the button can be reused for the cancellation of many different Tasks.

Answer 1

Instead of subscribing and unsubscribing from the click event, call your cancelTask from your click-event

private void stopButton_Click(object sender, EventArgs e)
{
    var handler = cancelTask;
    if (handler != null) {
        handler(this, _task, _cancelSource);
    }
}

and subscribe and unsubscribe from cancelTask

cancelTask += Whatever;
cancelTask -= Whatever;