The unresolved external symbol error occurs during the VC ++ program compilation connection.

Usually debug is used for debugging, while release is used for release. Some settings made under debug are not set under release, resulting inProgramCompilation fails. Be sure to pay attention later.

One of my vc ++ programs uses the dynamic link library (DLL), which is a: MFC extention DLL (using shared mfc dll ).

There is no problem in compiling in debug. You can change to release and an error will occur during compilation. The error is unresolved external symbol.

Finally, no lib file name is set for the object/library modules of release. I just need to add it.