Testing Events for Nothing/Null (Doug Rothaus)

re: Testing Events for Nothing/Null (Doug Rothaus)

Jordan — Tue, 13 Sep 2011 02:59:30 GMT

This code really doesn't even compile???? What is going on here?

re: Testing Events for Nothing/Null (Doug Rothaus)

cember makinası — Tue, 26 Jan 2010 00:13:51 GMT

could not help me get a code snippet immediately thanks

re: Testing Events for Nothing/Null (Doug Rothaus)

Yu Heng Zhou — Tue, 01 Dec 2009 00:51:16 GMT

it is really useful for me.

SolutionFoundEvent is a hiden member, haha!

re: Testing Events for Nothing/Null (Doug Rothaus)

help — Thu, 15 Oct 2009 17:13:26 GMT

Any idea what to do if you assigned an eventhandler and it is still nothing?

I had four event handlers assigned that work, then added a fifth in the same location that always shows up as Nothing. The others still work properly and keep their pointers.

(using ASP.NET 3.5 sp1 with VB, by the way)

re: Testing Events for Nothing/Null (Doug Rothaus)

DeWolf — Thu, 15 Oct 2009 10:18:17 GMT

I might be missing the point here, but why not use a custom event. A RaiseEvent accessor is used in a custom event to specify the statements to execute when the event is raised using the RaiseEvent statement. Typically, this invokes a list of delegates maintained by the AddHandler and RemoveHandler accessors. But this can also be used to check for Nothing.

re: Testing Events for Nothing/Null (Doug Rothaus)

Waleed El-Badry — Mon, 05 Oct 2009 09:06:50 GMT

Thanks Doug,

It was really useful to me.

re: Testing Events for Nothing/Null (Doug Rothaus)

VBTeam — Thu, 01 Oct 2009 23:28:01 GMT

Changed "public" to "private". Thanks for the catch.

re: Testing Events for Nothing/Null (Doug Rothaus)

Chance — Thu, 01 Oct 2009 22:27:28 GMT

"...it creates a public variable for the event.."

Not really. It creates a private member in the class.

re: Testing Events for Nothing/Null (Doug Rothaus)

Héctor — Wed, 30 Sep 2009 13:13:56 GMT

I was already aware of this, but since the VB compiler already adds the code and checks for you is not like in C# where this is a common practice. So I wonder... when is this actually needed? never found a situation where the event variable is nothing.

re: Testing Events for Nothing/Null (Doug Rothaus)

Nah — Tue, 29 Sep 2009 10:55:38 GMT

Is this really a good idea?

I would expect the behaviour to be exactly the same if there is no event handler as if there is one that ends up doing nothing.

The only "safe" use I can imagine is perhaps skipping some checks after the event that you otherwise would have to do in case something was changed during the event.