I recently worked on a project where we were able to compile and run the Silverlight Business App, but none of the breakpoints were working. We added a breakpoint in the Silverlight code, as well as, one in the RIA code but code was not breaking while debugging. The resolution was simple...only if you knew where to tweak!
Step1: Is the Silverlight added in your debug-able list?
Lets to go SolutionExplorer, Right click on the Silverlight's hosting project (xxxx.web), Click on Properties, Click on Web: Make sure Silverlight Checkbox is selected:
Step2: Is the Silverlight project tied to your Web project?
Go to Solution Explorer, Right click on the Silverlight's hosting project (xxxx.web), Click on Properties, Click on Silverlight Application: If Silverlight project has not been added, add it here.
Try debugging, your breakpoints should be hitting now!