Raising events from a dynamically loaded user control.

Question

I dynamically load a UC in the Oninit of the host page.

In the Oninit of the UC, I raise an event. I get a null reference exception. The code is as below:

//In the UC

public event CommandEventHandler DoneProcessing;
protected override void OnInit(EventArgs e)
{
      //Raise a event
      CommandEventArgs cmdEventArgs = new CommandEventArgs("done", "test");
      DoneProcessing(this, cmdEventArgs);
}

When I raise the event in Page Load instead of Oninit, it works fine, but I cannot do this since I have to load a child control and for things to work correctly (viewstate etc), I need to do this on OnInit.

Answer 1

It's a best practice to always to a null check before raising an event, in case there are no handlers.

if (DoneProcessing != null) {
    DoneProcessing(this, cmdEventArgs);
}

Answer 2

I believe you are attempting to do Event Bubbling. Here is an Ode to Code Reference called Event Bubbling From Web User Controls in ASP.NET (C#)

As already mentioned I suspect you can stop the error by using the standard

if (DoneProcessing != null) 
    DoneProcessing(this, cmdEventArgs);

However I think the root of to problem still has to do with the way the page is loaded. There are hacks around it but the "proper"(or recommend) way to do this is Event Bubbling.