Check your dll project and verify its set to build a Debug version and not a Release version. Moreover, If I'm not mistaken, I think you have to reference the dll the folder it was created in (i.e. < Project dir >\bin\Debug). If you have copied the dll to another location, and your application which uses it, is referencing the new copy at the new location, it probably won't identify your source code. Again... Not sure of it... :doh: Good luck, Shy.