If you ever need to access the MainPage object of your Silverlight application (from elsewhere in that application), simply do this where needed:
MainPage mainPage = App.Current.RootVisual as MainPage;
Bonus Tip: Don't be hesitant to look at the code generated by Visual Studio. I found out wthat the
RootVisual property represents the
MainPage object and is set when the application is started. Once I discovered that, the rest was easy.
