Question

This is something that I have never fully grasped in .NET as to the correct application of the .dispose() method.

Say I have something like

Public Class someClass()   sub someMethod     ' do some stuff tying up resources   end sub End Class  public class mainApp    dim _class as new SomeClass   _class.someMethod() End Class 

In all cases is it good practice to implement a dispose method, and if so what should go in there?

If it is not the case that every class should have dispose method (which my gut feeling says the shouldn’t) what classes should? I have always thought anything which may tie up a resource (i.e. connection, datareader etc) should have a .dispose() which would unallocate these resources.

Also how would you enforce a calling into calling the .dispose() method?

Answer 1

I highly recommend reading Cleaning Up Unmanaged Resources on MSDN, it has articles touching on when to use Dispose and how to implement IDisposable correctly. Your gut instinct is mostly correct as you rarely have to implement IDisposable, unless your class uses unmanaged resources or is a container for an object that implements IDisposable.

As to enforcing the calling of Dispose, when you properly implement the IDisposable interface you attach a finalizer which calls Dispose to catch those stragglers and deviant classes that forgot.

Relevant articles:

Implementing a Dispose Method

Describes the implementation of the Dispose method for releasing unmanaged resources.

Using Objects That Encapsulate Resources

Describes ways to ensure that the Dispose method is called, such as the C# using statement (Using in Visual Basic).

(edit: additional information added)

In your example you have SomeClass.SomeMethod which does some work, presumably with a resource. If this resource isn’t a class member, you may be better served wrapping it in a using-statement, and forgetting about the devilish details of IDisposable.

Public Class someClass()   sub someMethod     Using someResource As New ResourceType( arguments )        ' no worries about IDisposable for someResource, as it is automatic     End Using   end sub End Class