There is no source available for the current location

Open "Solution 'YourSolutionName' property pages" window (go to main menu: Project->Properties) and then go to "Debug Source Files". Check under "Do not look for these source files" window if you have your problematic file path written in it. If yes, delete the path and try again. I think this might solve your problem.

Regards,

Likely what is happening, is that DLL that you've referenced is throwing an exception when you're calling it. When you're debugging, Visual Studio would like you show you the line of code that is throwing the error, but it doesn't know where the source is. Usually, in my environment, it will prompt you to locate the source file and open it so that it can show you additional debug information. I would usually get the error you mention, when I press cancel on that dialog since I either don't have the source, or don't care what the source is