what does warning C4251 class needs to have dll interface to be used by clients of class mean?

[Steve Richter]

what does C4251 class needs to have a dll interface warning mean?

Warning 1 warning C4251: 'reg::RegPartBase::mPartText' : class 'std::basic_string<_Elem,_Traits,_Alloc>' needs to have dll-interface to be used by clients of class 'reg::RegPartBase' c:\srcpp\libfilepreview\x64\debug\RegPart.h 32 1 LibFilePreview

I have a class in a DLL. In the project that uses the DLL there is a header file that declares the class with __declspec(dllimport).


class __declspec(dllimport) RegPartBase
{

public:
wstring mPartText ;
PartType mPartType ;
...
} ;






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