What's the point of overriding Dispose(bool disposing) in .NET?

c# .net dispose idisposable
Mark Carpenter picture Mark Carpenter · Feb 25, 2009 · Viewed 33.1k times · Source

If I write a class in C# that implements IDisposable, why isn't is sufficient for me to simply implement 

public void Dispose(){ ... }

to handle freeing any unmanaged resources?

Is

protected virtual void Dispose(bool disposing){ ... }

always necessary, sometimes necessary, or something else altogether?

Answer

Jon Skeet picture Jon Skeet · Feb 25, 2009

The full pattern including a finalizer, introduction of a new virtual method and "sealing" of the original dispose method is very general purpose, covering all bases.

Unless you have direct handles on unmanaged resources (which should be almost never) you don't need a finalizer.

If you seal your class (and my views on sealing classes wherever possible are probably well known by now - design for inheritance or prohibit it) there's no point in introducing a virtual method.

I can't remember the last time I implemented IDisposable in a "complicated" way vs doing it in the most obvious way, e.g.

public void Dispose()
{
    somethingElse.Dispose();
}

One thing to note is that if you're going for really robust code, you should make sure that you don't try to do anything after you've been disposed, and throw ObjectDisposedException where appropriate. That's good advice for class libraries which will be used by developers all over the world, but it's a lot of work for very little gain if this is just going to be a class used within your own workspace.

Related questions

How does one tell if an IDisposable object reference is disposed?

Is there a method, or some other light-weight way, to check if a reference is to a disposed object? P.S. - This is just a curiousity (sleep well, not in production code). Yes, I know I can catch the …

Read More
How and when are c# Static members disposed?

I have a class with extensive static members, some of which keep references to managed and unmanaged objects. For instance, the static constructor is called as soon as the Type is referenced, which causes my class to spin up a …

Read More
Dispose, when is it called?

Consider the following code: namespace DisposeTest { using System; class Program { static void Main(string[] args) { Console.WriteLine("Calling Test"); Test(); Console.WriteLine("Call to Test done"); } static void Test() { DisposeImplementation di = new DisposeImplementation(); } } internal class DisposeImplementation : IDisposable { ~DisposeImplementation() { Console.WriteLine("~ …

Read More