Eric Wise

Business & .NET

Set foo = Nothing?

It's my understanding that because the .NET Garbage collector looks at the heap, and checks to see if any variables on the heap are in scope that setting an object to nothing at the end of a function in VB .NET really doesn't gain you anything yet I see code like this often:

Try

'Do Stuff

Catch

Finally

'Set a bunch of objects = Nothing

End Try

Is there a valid reason to do this in your methods that I'm missing? Or is this just a habitual holdover from VB 6.0 programmers?

Published Jul 29 2004, 10:48 AM by Eric Wise

Comments

Dave Truxall said:

I have the same question. I keep seeing it in other developer's code, but like you I thought it was unnecessary. I thought the only objects you needed to address in the finally clause were ones that implmented IDisposable or interfaced with unmanaged resources.

# July 29, 2004 7:45 AM

Rob Teixeira said:

It is habitual programming. There is no need to set a *local* variable to nothing, as the reference will be wiped off the stack when the function ends and unwinds the stackframe. Assuming the heap object data for that reference has no other references, the GC will take care of it later.

However, your Finally block *should* properly call Dispose or Close for objects containing unmanaged resources. Only a percentage of objects have a Dispose or Close method, so it's not something you have to do for everything, and certainly not for entirely-managed objects that you write.

# July 29, 2004 8:09 AM