CODEWITHSUNDEEP
c#.netgarbage-collectiondestructor
Ali Kherad
Ali Kherad

Reputation: 965

Is it possible to determine an object being disposed right after last object reference freed up?

I'm creating a Memory holder class that wraps around a heap object, and I want to determine the dispose of the object is very force for GC.

I want something like:

myObj = null; //Immediately call to ~myObj()

Upvotes: 0

Views: 69

Answers (3)

supercat
supercat

Reputation: 81159

COM objects expect to be notified promptly when they go out of scope, but .NET does not support prompt notification except via Dispose. You should call IUnknown.Release in your dispose method but you must ensure before calling IUnknown.Release that there is no way that anyone might ever try to use that COM object again. Attempting to use a COM object that has after Release, or even simply trying to call Release upon it again, is a recipe for disaster.

I would suggest, therefore, that no reference to the COM object itself ever be released to outside code. Instead, have the class which holds the object forward all requests to the object itself within a lock (to ensure that code doesn't attempt simultaneous accesses), and have your Dispose method acquire the lock, call Release on the object, and then invalidate the reference. Any future attempts to manipulate the object which aren't otherwise trapped will cause a NullReferenceException which isn't brilliant, but is still way better than trying to use a COM object after it is released.

Upvotes: 0

Sam Harwell
Sam Harwell

Reputation: 99869

The .NET framework and runtime provides two features for applications which use unmanaged resources.

  1. Deterministic cleanup: The IDisposable interface allows code to release resources at a specific time, by explicitly or implicitly calling the Dispose() method. (The using statement in C# provides implicit support for this call.)
  2. Eventual cleanup: In the event users fail to release unmanaged resources by calling the Dispose() method, a finalizer can be used to prevent long-running applications from leaking these resources over time. User code generally should not include user-defined finalizers; instead, create (or use an existing) class which extends SafeHandle and implement the ReleaseHandle method to define the release behavior.

Note that IDisposable.Dispose() is the only supported mechanism for deterministic resource cleanup. Eventual cleanup is a non-deterministic fallback that should be avoided.

Upvotes: 2

Tim S.
Tim S.

Reputation: 56536

No, you can't do this. You should simply use IDisposable as it's meant to be used.

Upvotes: 2

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