unresolved external symbol for structures in cpp?
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I know most of time you get UNRESOLVED EXTERNAL SYMBOL for not including library or for not correctly defining function in class, but i get same error for structure.
I have few files .cpp and .h in one of the .h i have defined 

    extern struct MyDataStruct StructData;

I include this .h in my .cpp file but i get 

    'struct MyDataStruct StructData' unresolved external symbol

I define this structure out of any class and i access it without any class prefix.

Thanks in advance.