What have you tried? From what I can say from the source, there should be something like:
<UserControl ... xmlns:tk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/toolkit"> <tk:WrapPanel/> </UserControl>
Note that it doesnโt really matter if they changed assemblies or even namespaces because they have mapped the corresponding CLR namespaces to http://schemas.microsoft.com/winfx/2006/xaml/presentation/tools.
source share