Adding __declspec(dllexport) breaks linkage of my static library

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VS2010

I have a VS 2010 solution with two C++ projects. One produces an application (.exe). The other produces a static library (.lib). The application uses the static library. The solution builds and the application executes as expected. The class is declared as follows.

class MyClass
{
public:
static void MyFunc(void);
};

if the class declaration is changed as follows:

class __declspec(dllexport) MyClass
{
public:
static void MyFunc(void);
};

The application (.exe) build fails with the following error message.

.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: static

Why ?

What I have tried:

searched the web and did not find an explanation