The vicious deadlock situation (the one that does not freeze the GUI but leaks memory)

This post is dedicated to windows forms UI deadlock situations.

I) The classical deadlock situation (the one that freeze the UI)

This happens when the synchronization with the UI thread is made in a synchronous manner (Control.Invoke(...), SynchronizationContext.Send(...) etc.).
Solution: To fix this kind of deadlock, you may use asynchronous API to delegate tasks execution to the UI thread.

Those asynchronous API may be :

• System.Threading.SynchronizationContext.Post(...)
• Control.BeginInvoke(...) - but this may require too much CPU due to the underneath .NET reflection usage - I'll write a post on that topic later)
• ...
  

II) The vicious deadlock situation (the one that does not freeze the UI but leaks memory)

This kind of deadlock is slightly more difficult to diagnostic. It happens when a "non UI" thread is making a call to the Invoke method of a Control that belongs to a closed Windows Form (this may happen just after a close to the Form).

In that case, the execution blocks indefinitely on the call to Control.Invoke() and the delegate supply to it never begins (see here). => this prevent the lock from being released by the blocked thread !

Solution: Prevent from situations where "zombie controls" are accessed (beware to unsubscribe all the .NET events to prevent from maintaining object alive) and use one of the asynchronous API to delegate tasks execution to the UI thread.