Why is it preferred to not use finalize for clean up? .NET

Question

(Windows API created objects, File, Database connection objects, COM objects, etc.) are outside the scope of .NET Framework. We have to explicitly clean our resources. For these types of objects, .NET Framework provides Object.Finalize method, which can be overridden and clean up code for unmanaged resources...

1. Why is it preferred to not use finalize for clean up?

2. What is appropriate to use?

Answer 1

The preferred way is to implement IDisposable along with the dispose pattern. Finalizers are time-limited and the GC will terminate a finalizer if it blocks for too long - this is the primary reason to avoid it where possible.

Dispose is just a method call and is not time-limited. The dispose pattern optionally features the finalizer for those situations where the caller forgot to call Dispose (as it's not enforced) as a last-ditch attempt to release resources. The pattern also suppresses the finalizer if dispose was called.

The only valid use I have come across with needing a finalizer was for a series of add-ins I wrote for a third party app that didn't raise relevant events for properly managing object life-times. I used the finalizer to make sure I at least attempted to clean stuff up. Other than this I have never relied upon it directly.

IDisposable is catered for in C# with the using keyword. Anything implementing this interface can be used thus:

using (var myDisposableItem = new MyDisposableItem())
{
} // Dispose will be called here for you.

So from the calling perspective this is very simple.

_{There are various types in the .NET Framework that implement IDisposable but have nothing to dispose. I always advise acting as if they need disposing directly because the public contract states they have stuff to dispose, even if the implementation doesn't. Don't program to implementation details.}