Simply install the VS2010 SP1 and Silverlight 5 Beta and you get the unexpected bonus of the XAML Parser supporting debugging your data bindings for your Silverlight 4 projects. As SL5 sits nicely in VS2010 SP1 with SL4 it is worth installing the beta just for this feature.
I was at the @SLUGUK meeting 18th May 2011, and as Mike Taulty pointed out for other ‘features’, it is difficult to know whether such things as this were introduced by the service pack or the beta as nobody seems to have stopped to check in the rush to get the SL5 beta working 🙂
Checked against the NoDo Windows Phone 7 projects and it does not work, you can set a breakpoint but it cannot resolve the symbols. The new feature automatically creates the symbol names for you. I am optimistic that this feature will work with the Mango tooling to be released by end of May 2011 (that’s next week) [UPDATE: Mango beta no Xaml debugging for now].
No point in re-documenting the feature so:
Mike Taulty’s Blog: Silverlight 5 Beta Rough Notes – Debugging Data-Binding
Code Project: Debugging Data Bindings in XAML with SIlverlight 5 Beta