I have a Windows Service that uses a plugin architecture for some things. I couldn’t figure out why I couldn’t step through one of the plugin modules. I checked that my plugin system wasn’t actually running in a separate app domain (not that it should matter) and it wasn’t. I have that set as a runtime configuration option, but no, only one app domain here. I scratched my head some more and took a look at my plugins directory. DUH! I stopped copying the pdb files (the debug symbol files) on build.
So if you run into the dreaded “cannot find source”, just remember that you must have the pdb files along side the dlls.
I didn’t find much when googling for this except for this link: