Re: Simple Dispose Question

From: Jeffrey Palermo, MCAD.Net (jeffreypalermo_at_gmail.com)
Date: 02/24/05 

Date: 24 Feb 2005 06:16:19 -0800

Jeff,
I'd like to add something that hasn't come out in this thread yet. The
use of .Dispose() has been thoroughly discussed, but I'd like to answer
your question regarding the benefit of additionally setting the
variable to null.

If I assume that you have a method containing only that code:
void Foo(){
DataAdapter da = null;
try {
  // Some logic here...
} catch (Exception ex) {
  // Some exception handling logic here...
} finally {
  // Clean up...
  if (da != null) {
    da.Dispose();
    da = null;
}
}
you are setting da to null one statement before it would naturally be
set to null (or go out of scope). At the end of every method, every
variable declared in the method is set to null and goes out of scope,
so there is no benefit of explicitly setting it to null because it will
automatically happen one statement later.

On the other hand, there are situations where if may be beneficial to
set this to null. For instance:
void Foo(){
    DataAdapter da = new DataAdapter(. . .);
    try{
    // use it somehow
    }finally{
    da.Dispose();
    }
    // now call another method that may take a while to return
}
Here, we would wait for another long-running method to return and the
da variable would still be in scope. Depending on what the
long-running method does, the GC may run several times. IN THIS CASE,
if you set da to null just before calling the long-running method, any
garbase collections would be able to reclaim that memory, and you would
have a benefit.

Normally, my methods are small enough that my variables naturally go
out of scope quickly, but in cases where they might not, set it to
null.

Best regards,
Jeffrey Palermo
Blog: http://www.jeffreypalermo.com

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