Here is an answer from a similar question
1) PDB files are not up to date. Try to uncheck Tool->Options->Debugging->General->"Require source files to exactly match the original version"
2) You've referenced another of your projects byadding it's dll to your references instead of adding the project as reference. Try to remove the reference add add a new reference to the project from the "Projects" tab
Answered by - Simon Bang Terkildsen
check out this link here for complete discussion: There is no Source code available for the current location. in ASP .net
Let me know if it worked. If not I will try to give you some more pointers on what could be wrong.