How do I fix the inexplicable "Item has already been added" errors with XAML?

I have been updating soem Silverlight 1.0 demo's to Silverlight 2 and came across this regular error. Its caused by a duplication of namespaces (e.g. UserControl redefines the namespace for its Canvas)

Fix is therefore pretty easy:

1) You need to search for any xmlns attributes in your XAML and delete them

2) Clean or Rebuild in Studio

Skip to main content