Question

Possible Duplicate:
Any sense to set obj = null(Nothing) in Dispose()?

I understand if this question is closed as a duplicate, but I’m having some trouble reconciling some posts on this topic.

First a little background. I have a class Foo as follows

public class Foo : IDisposable
{
    private Dictionary<int, string> _reallyBigDictionary = 
            new Dictionary<int, string>();

    public void Dispose()
    {
        _reallyBigDictionary = null;
    }
}

Instances of Foo are known to have a limited scope (i.e. I know we’re not keeping it around forever). Given it’s instance’s limited scope, I don’t see how nulling out _reallyBigDictionary actually frees up memory sooner than the dispose. The way I understand it, these objects won’t ever get cleaned up until garbage collection is run. At that time, references to the given instance of Foo will be null regardless, so I expect GC to reclaim that memory regardless.

These posts lead me to believe that there is no point in setting member variables to null:

Memory leak problems: dispose or not to dispose managed resources?

Is it better to destroy all objects or just let the garbage collector do the job?

This post makes me question otherwise:
Proper use of the IDisposable interface

Can anyone clarify this point for me? Is the IDisposable implementation really necessary here? Because I just can’t convince myself it is.

Answer 1

You don’t need IDisposable; here’s why. In summary, you need to follow Rule 1: Don’t implement IDisposable unless you need to.

There are only two situations when IDisposable does need to be implemented:

• The class owns unmanaged resources.
• The class owns managed (IDisposable) resources.

Since Dictionary<int, string> is not IDisposable, your class shouldn’t be either.