I have seen in the output-Window of Visual Studio, that there occurs many times the Message
A first chance exception of type 'System.Xml.XmlException' occurred in System.Xml.dll
When I fill the DataGrid (Xaml/WPF - DevExpress DXGrid). Does anybody know why this is?
http://blogs.msdn.com/b/davidklinems/archive/2005/07/12/438061.aspx
Maybe this helps you further.
Edit
Based on your comment on your question, I assume, that you are interested in finding a bottleneck in your application.
This link leads to a video I liked much to learn how to find bottlenecks in WPF-Apps.
The WPF Performance Toolkit is a free toolkit with programms to measure WPF-performance. It will help you to find the problem if it is in the visualization.