Use of Finalize/Dispose method in C#

Question

C# 2008

I have been working on this for a while now, and I am still confused about the use of finalize and dispose methods in code. My questions are below:

Answer 1

I agree with pm100 (and should have explicitly said this in my earlier post).

You should never implement IDisposable in a class unless you need it. To be very specific, there are about 5 times when you would ever need/should implement IDisposable:

1. Your class explicitly contains (i.e. not via inheritance) any managed resources which implement IDisposable and should be cleaned up once your class is no longer used. For example, if your class contains an instance of a Stream, DbCommand, DataTable, etc.

2. Your class explicitly contains any managed resources which implement a Close() method - e.g. IDataReader, IDbConnection, etc. Note that some of these classes do implement IDisposable by having Dispose() as well as a Close() method.

3. Your class explicitly contains an unmanaged resource - e.g. a COM object, pointers (yes, you can use pointers in managed C# but they must be declared in 'unsafe' blocks, etc. In the case of unmanaged resources, you should also make sure to call System.Runtime.InteropServices.Marshal.ReleaseComObject() on the RCW. Even though the RCW is, in theory, a managed wrapper, there is still reference counting going on under the covers.

4. If your class subscribes to events using strong references. You need to unregister/detach yourself from the events. Always to make sure these are not null first before trying to unregister/detach them!.

5. Your class contains any combination of the above...

A recommended alternative to working with COM objects and having to use Marshal.ReleaseComObject() is to use the System.Runtime.InteropServices.SafeHandle class.

The BCL (Base Class Library Team) has a good blog post about it here http://blogs.msdn.com/bclteam/archive/2005/03/16/396900.aspx

One very important note to make is that if you are working with WCF and cleaning up resources, you should ALMOST ALWAYS avoid the 'using' block. There are plenty of blog posts out there and some on MSDN about why this is a bad idea. I have also posted about it here - Don't use 'using()' with a WCF proxy