What happens to Monitor.Enter without a matching Monitor.Exit?

Question

If you have some blocks of code that you would like to prevent execution of when the object is being exited and cleaned up, could a lock be used to prevent the execution?

Monitor.TryEnter(cleanupLock, ref acquiredLock);

TryEnter could be used to ensure that the code is not executed, and since it does not wait for the lock there will not be a deadlock.

Another thread would grab the lock when it determines that it is time for shutdown.

Monitor.Enter(cleanupLock);

If the cleanup thread never calls

Monitor.Exit(cleanupLock);

would this cause a problem?

Answer 1

Yes, not calling Monitor.Exit for a succesful Monitor.TryEnter or Monitor.Enter is a fast track to a deadlock in your application. You may be able to get it to work in a very limited scenario but eventually the code or scenario will change and this will come back to bite you. Just don't do it.