Setting Objects to Null/Nothing after use in .NET

Should you set all the objects to `null` (`Nothing` in VB.NET) once you have finished with them?

I understand that in .NET it is essential to dispose of any instances of objects that implement the `IDisposable` interface to release some resources although the object can still be something after it is disposed (hence the `isDisposed` property in forms), so I assume it can still reside in memory or at least in part?

I also know that when an object goes out of scope it is then marked for collection ready for the next pass of the garbage collector (although this may take time).

So with this in mind will setting it to `null` speed up the system releasing the memory as it does not have to work out that it is no longer in scope and are they any bad side effects?

MSDN articles never do this in examples and currently I do this as I cannot
see the harm. However I have come across a mixture of opinions so any comments are useful.

The only time you should set a variable to null is when the variable does not go out of scope and you no longer need the data associated with it. Otherwise there is no need.

Also:

using(SomeObject object = new SomeObject())
{
// do stuff with the object
}
// the object will be disposed of

There are some cases where it makes sense to null references. For instance, when you're writing a collection--like a priority queue--and by your contract, you shouldn't be keeping those objects alive for the client after the client has removed them from the queue.

But this sort of thing only matters in long lived collections. If the queue's not going to survive the end of the function it was created in, then it matters a whole lot less.

On a whole, you really shouldn't bother. Let the compiler and GC do their jobs so you can do yours.

In general, there's no need to null objects after use, but in some cases I find it's a good practice.

If an object implements IDisposable and is stored in a field, I think it's good to null it, just to avoid using the disposed object. The bugs of the following sort can be painful:

this.myField.Dispose();
// ... at some later time
this.myField.DoSomething();

It's good to null the field after disposing it, and get a NullPtrEx right at the line where the field is used again. Otherwise, you might run into some cryptic bug down the line (depending on exactly what DoSomething does).

Chances are that your code is not structured tightly enough if you feel the need to *`null`* variables.

There are a number of ways to limit the scope of a variable:

As mentioned by **Steve Tranby**

using(SomeObject object = new SomeObject())
{
// do stuff with the object
}
// the object will be disposed of


Similarly, you can simply use curly brackets:

{
// Declare the variable and use it
SomeObject object = new SomeObject()
}
// The variable is no longer available

I find that using curly brackets without any "heading" to really clean out the code and help make it more understandable.