Refresh WPF Command

Calling System.Windows.Input.CommandManager.InvalidateRequerySuggested() forces the CommandManager to raise the RequerySuggested event.

Remarks: The CommandManager only pays attention to certain conditions in determining when the command target has changed, such as change in keyboard focus. In situations where the CommandManager does not sufficiently determine a change in conditions that cause a command to not be able to execute, InvalidateRequerySuggested can be called to force the CommandManager to raise the RequerySuggested event.

I was aware of CommandManager.InvalidateRequerySuggested() a long time ago, and used it, but it wasn't working for me sometimes. I finally figured out why this was the case! Even though it doesn't throw like some other actions, you HAVE to call it on the main thread.

Calling it on a background thread will appear to work, but sometimes leave the UI disabled. I really hope this helps somebody, and saves them the hours I just wasted.