Question

I have a .NET 3.5 WPF application on Windows 7 64bit. I am experiencing odd system freeze issue that happens when dragging and moving the main application window. Basically the entire system freezes (UI) and the application stops rendering.
Bringing up the task manager (CTRL+ALT+DEL) unfreezes both system and the application.

The application itself is a trading application that processes a large amount of messages in background threads.

Has anyone experienced this type of issues ? Especially the oddity of task manager unlocking the freeze. What could be the reason for this strange behavior?

I am almost certain it has something to do with dispatching certain actions to the UI thread.

Answer 1

The issue was WCF service deadlocking. Issue similar to this

In the service that processed messages incoming messages had to be added on the UI thread to the collection the following way.

Action action = new Action(() =>
            {
                lock (_messagesLock)
                {
                    _messages.Remove(message);
                }
            });
            _dispatcher.Invoke(DispatcherPriority.Normal, action);

Changing

_dispatcher.Invoke(DispatcherPriority.Normal, action);

To

_dispatcher.BeginInvoke(DispatcherPriority.Normal, action);

Solved the issue.