(dll)export symbols

Hello!
I am a little bit confused. I write this article only for clarity. Here are my questions.
When do i have to use a factory method and when (dll)export/import for my class. I know that i have to use a factory method (declared with extern "C") when i load a library file and the symbols explicit with dlopen and dlsym. But does i need a factory method if i load the library file implicit? My opinion is that i dont need this function and i can declare the class with (dll)export/import. The only exception is that the header file, that contain such a class, includes some header(s) or something else that should not be declared in the file i use the library. Is this right? I know that it is possible to declare a class in VC++ with dllexport. Is this also possible with gcc?
(is there a reference document covering this topic?)

Thanks in advance