Conflicting x:Name properties in different XAML files
RadWindow works by inserting a Canvas which holds the content of the window in the top-most panel of the application. This has an important consequence that can
catch people off guard if they are not aware of it.
Consider an application that has a main page, and, for example, a UserControl that represents some part of the main page UI. If for some reason the user control
contains a window which contains an element with a name, say x:Name="myElement" and the main page also has an element with x:Name="myElement" Silverlight will complain. This
happens because the "myElement" which is inside RadWindow is inserted in the same element tree at run-time as the other "myElement" on the main page, more concretely, it is
inserted in the top-most panel of the application. Now the RadWindow "myElement" is above the main page "myElement" and Silverlight can not have two elements with the same name in
the same element tree. The solution is simply to choose unique names when populating RadWindow with content.
Using windows inside windows
RadWindow does not support opening windows inside windows for two reasons. One of those reasons is that a popup over a popup can dramatically increase the fill rate of the application
leading to performance degradation. The second reason is that the Metro design language does not encourage this UI pattern. Only one popup should be open at any time. If more popups need
to be open the application usability designer should consider displaying the other popups on separate pages.