[vtkusers] custom vtkInteractorStyle ??!

[imho]

Hi,
I try to create my own subclass from vtkInteractorStyle. But I 've got a 
linkage error on visual c++ :

vtkInteractorStyleCustom.obj : error LNK2001: unresolved external symbol 
"public: virtual char const * __thiscall 
vtkInteractorStyle::GetClassNameW(void)" 
(?GetClassNameW at vtkInteractorStyle@@UAEPBDXZ)


What can I do?

thanks a lot!