C# Monitors [modified]

[manustone]

Hi all I'm new to C# multithreading and I read that to resolve deadlock it is best to use monitor with timeout.With this in mind I used the following code to see what happens to the deadlocking generated. The result is the following exception Unhandled Exception: System.Threading.SynchronizationLockException: Object synchronization method was called from an unsynchronized block of code. Why this? What's wrong with my code or my approach? Regards manuStone class ThreadFoos { public static void First() { Monitor.TryEnter(ResourceA, 1000); try{ Thread.Sleep(500); Monitor.TryEnter(ResourceB, 1000); try{ Console.WriteLine("First"); } finally{ Monitor.Exit(ResourceB); } } finally{ Monitor.Exit(ResourceA); } } public static void Second() { Monitor.TryEnter(ResourceB, 1000); try{ Thread.Sleep(500); Monitor.TryEnter(ResourceA, 1000); try{ Console.WriteLine("Second"); } finally{ Monitor.Exit(ResourceA); } } finally{ Monitor.Exit(ResourceB); } } private static object ResourceA = new Object(); private static object ResourceB = new Object(); }

[gnadeem]

hi there. this is what i think. to start with http://msdn2.microsoft.com/en-us/library/system.threading.monitor.exit.aspx[^] which implies that Monitor.Exit can be called on a thread , for a resource only if that thread has already acquired lock for that resource. you are calling Monitor.Exit (one out of try statements) on threads without assuring that a thread has already successfully acquired monitor on a specified resource. (i.e Monitor.TryEnter may not have been successfull). please Check the returned value from Monitor.TryEnter for both 'First' and 'Second' rountines. regards.

[manustone]

Thank you very much for your resposne. Have a nice day. Regards manuStone