Can't link your library...?

Do you have new class and for forgot to fully implement it...?

e.g.
you have an error like this

MyLib.lib(MyClass.obj) : error LNK2001: unresolved external symbol "public: virtual long __stdcall MyNamespace::MyClass::SomeMethod(...)

MyClass.h declares
void SomeMethod();

and in
MyClass.cpp

you only put
void SomeMethod()
{
}

Looks okay, doesn't it?

it is close, but needs the class name for scope resolution
i.e.
void MyClass::SomeMethod()
{}