Raising an Event -- Object reference not set to an instance of an object

I'm getting the error:
System.NullReferenceException: Object reference not set to an instance of an object.
The code is below, and the error is on the line that I've indicated with arrows.
Why is this? I can't see what I'm doing wrong. Is this not how you raise an event?
I practically copied this example http://www.akadia.com/services/dotnet_user_controls.html.
Please help!
Thank you.

//this is my web form
namespace TestWebApp
  public class MyWebForm : System.Web.UI.Page
    protected MyControlNS.MyControl MyControl;
    private void Page_Load(object sender, System.EventArgs e)
      MyControl = new MyControlNS.MyControl();

//This is my web control
namespace MyControlNS
  public class MyControl : System.Web.UI.WebControls.WebControl
    public delegate void EventHandler(Object sender, EventArgs e);

    public event EventHandler MyEvent;

    public int TestEvent()
      MyEvent(this, new System.EventArgs()); // <---- <---- <----
      return 1;
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

I normally do it something like this:

this.TextBox1.Leave += new System.EventHandler(this.TextBox2_Leave);

private void maskedTextBox2_Leave(object sender, System.EventArgs e)
      //Your code here!

Hi jini555,

The problem is the following .......

you can raise an event, only when it has a handler associated to it, otherwise, as you said, it will throw the  
"Object reference not set to an instance of an object" exception.

In order to avoid this, you can do the following

if( MyControl.TestEvent != null )

in this way, you'll first avoid the case when testevent is null (does not have any handler associated).
Besides, what's the use of throw an event if it does not have any handler associated to it.

and will be thrown when it has someone who will listen to it.

Hope this helps!


Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Just a quote from Programming C# 2nd Edition (O'Reilly)


It then notifies the subscribers by firing the OnSecondChange event:

// if anyone has subscribed, notify them
if (OnSecondChange != null)

If an event has no subscribers registered, it will evaluate to null. The test above checks that
the value is not null, ensuring that there are subscribers before calling OnSecondChange.


CompTIA Network+

Prepare for the CompTIA Network+ exam by learning how to troubleshoot, configure, and manage both wired and wireless networks.

jini555Author Commented:
thank you VERY MUCH for taking the time to explain clearly. I am at home right now, but when I get into work tomorrow, I will make that small change.
I'll get back to you afterwards.

Thank you for your input as well. I wanted to merely understand the bug in my code rather than do it another way. :)

hope that solves all you need.

jini555Author Commented:
sorry for the delay, something came up and i was away.

anyways, yes, that error is gone now :).

i should note, however, that i could not compile it without removing the "event" keyword. According to this article I just found, (which i think might be the one you quoted)


the "event" keyword prevents another class from accessing the delegate with an operator other than += and -= . So -- I will check for null *inside* my control, rather than from the web form.

Thank you,
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.