how can i extract possible requests from Navigation and handle them?

[makisVar]

i write in C# markup i want to know what are the string options in Navigation.SetRequest , i know "-" goes back and sends the selection from list but i want more options in case user make wrong selection by mistake...Also i want to check if there is a request so it is not a default to go back on selection or anything else...More samples in c# markup in general would help a lot thanks! also a small implementation of IRequestHandler and IRouteNotifier could be neat