Question

we have a UserControl to handle User cancellations, that is used in a few places. This has a couple of input fields and a submission button. When they submit the User’s status is updated and a few other things are done and a feedback message displayed.

On one of the pages which includes the control, after the User has successfully cancelled their submission via the UserControl we need the page to be notified somehow so it can call one of its methods and update its display [in this case, the User’s status, which was attending and is now cancelled].

How do we link these up? I’d guess at something involving delegates and event handlers but don’t have much experience with them so don’t know if I’d be heading down a blind alley…

One very hacky solution would be for the UserControl to cause a re-direct and then have the page monitor the session or a query string parameter etc., but just typing it has made me shiver so would have to be very much a last resort.

If any more info is needed, please ask and I’ll provide it.

Answer 1

This should be pretty easy. Add a delegate event to your UserControl as follows:

public event EventHandler UserCancelled;

Then, in your user control at the end of the cancellation method, just call the delegate:

if (this.UserCancelled!= null)
{
   this.UserCancelled(this, new EventArgs());
}

Then, just add a handler to the event on your user control’s aspx markup:

OnUserCancelled="UserControl1_UserCancelled"

And finally, add a handler to your page:

protected void UserControl1_UserCancelled(object sender, EventArgs e)
{
    // Your code
}