I'm using Visual Web Developer 2008 Express + Silverlight 3 Tools + Silverlight 3 Developer runtime, debugging in Firefox 3.6.8.
When I create a Silverlight project and let the IDE set up an ASP.NET site to host it, the breakpoints will not be hit. If I create a single Silverlight project it will be fine. Something must be wrong when the IDE is pairing the two projects together.
I've tried many solutions on the net, none of them worked. (clearing firefox cache, rebuilding solution, tweaking project properties, reinstalling SL Tools/Runtime, adding Debug="true" to aspx file, etc.) The *.pdb file is clearly in the same folder of the output *.xap file.
Anyway if anyone can point me a direction it will be really great!
(BTW, one of solution involves loading symbols manually through "Debug > Window > Modules" window, however I couldn't find this window in design time or debug time. Is this a feature exclusive to non-Express editions?)
EDIT: Problem solved. Turns out it's the incompatibility with FireFox. Changed a config value and started a brand new solution (older solution still had problem), it finally worked.
Try running it in internet explorer - there might be bugs regarding attaching to firefox: http://forums.silverlight.net/forums/t/755.aspx