Look at this:
<ItemsControl ItemsSource="{x:Static local:Cache.Colors}" />
This binds the ItemsControl to a static property called List. In this case, the Colors property is part of a class called Cache.
But there is a problem. When you bind in this way, the Colors property is called during the Initialize method, prior to when Security is established in the application.
Because Security has not been established, then calling Colors results in an exception as Security is a requirement for successfully calling the data service.
The solution moves this from XAML to code behind and ensures it is executed in the Loaded event instead of in the constructor during Initialize.
The real problem here is, I would like to do this in XAML. Is it possible?
My solution was to run it in the App.xaml.cs before anything else.