My main solution is using code from a utility class library, that I wrote myself, but is a part from another solution. How can I set a breakpoint in the referenced DLL file?
Make sure you have the .pdb file in the bin/debug folder where the referenced class library dll resides. When you are debugging your current solution you should be able to step into the code from your class library. When you step into the class library you will be able to set breakpoints.