大家帮忙看下，怎么回事？
--------------------Configuration: Net - Win32 Debug--------------------Compiling...
msg.cpp
Linking...
msg.obj : error LNK2001: unresolved external symbol "public: virtual struct CRuntimeClass * __thiscall CMsg::GetRuntimeClass(void)const " (?GetRuntimeClass@CMsg@@UBEPAUCRuntimeClass@@XZ)Debug/Net.exe : fatal error LNK1120: 1 unresolved externals
执行 link.exe 时出错.
Creating browse info file...
Net.exe - 1 error(s), 0 warning(s)
请大家帮我看看，错在哪里了，我是手动加的msg.cpp和msg.h
