So far, we have seen that we can utilize a number of sources of information to help with tracking down the causes of our problems. However, what about actual debugging? In other GUI languages, we can add breakpoints at various locations in our code and watch our values changing as we step through our code. While we can also do this with WPF applications, it is not always so obvious where to put our breakpoints to ensure that program execution will hit them.

If you remember from the previous chapter, the CommandManager.RequerySuggested event is raised when the CommandManager detects a change in the UI that could reflect on whether a command could execute or not. Well, it turns out that two of the conditions that the CommandManager looks out for is when the application window is either activated or deactivated and we can take advantage of this to help us when debugging. Note that the application window is deactivated when the user moves focus from it and is reactivated...