class CShape
{
    // store serial number
public:
    static  int mnSerialNum;

    // constructor
    CShape();


    // function declaration
    virtual int getSerialNum();

    // create virtual pure function
    virtual double Area(double dWidth, double dHeight)      = 0;
    virtual double Perimeter(double dWidth, double dHeight) = 0;
    virtual void DisplayClassName();
};

error LNK2001: unresolved external symbol "public: virtual void __thiscall CShape::DisplayClassName(void)" (?DisplayClassName@CShape@@UAEXXZ)

how can i solve this error

/ i solved this error is in function defenition
so Check function declaration if this type of error
cpme