Why is only the UI thread allowed to modify the UI?

Question

I know that if I am modifying a control from a different thread, I should take care because WinForms and WPF don\'t allow modifying control\'s state from other threads.

Answer 1

Several GUI frameworks have this limitation. According to the book Java Concurrency in Practice the reason for this is to avoid complex locking. The problem is that GUI controls may have to react to both events from the UI, data binding and so forth, which leads to locking from several different sources and thus a risk of deadlocks. To avoid this .NET WinForms (and other UIs) restricts access to components to a single thread and thus avoids locking.