Prism's ItemsControl seems to have a xaml parse error. Why?

I am at a loss as to why my She开发者_运维技巧ll.xaml's ItemsControl is causing a parse error. I know the syntax is correct because I copied the Silvelright project files from a working project.

Right now my only guess is that ItemsControl is dependent on something else.

Here is the relevant xaml line for ItemsControl.

<ItemsControl x:Name="Region" 
                      VerticalAlignment="Center" 
                      HorizontalAlignment="Center" 
                      Regions:RegionManager.RegionName="Region"/>

i found that i wasn't Resolving my shell using unity. I had accidentally left it as VisualElement = new Shell.