使用举例： 
// File: SimpleDLLClass.h
#ifdef SIMPLEDLL_EXPORT //在DLL工程属性-c/c++-预处理器-预处理器定义中添加此宏定义
#define DLL_EXPORT __declspec(dllexport)
#else
#define DLL_EXPORT __declspec(dllimport)
#endif
class DLL_EXPORT SimpleDLLClass
{
public:
 SimpleDLLClass();
 virtual ~SimpleDLLClass();
 virtual getValue() { return m_nValue;};
private:
 int m_nValue;
};
// File:　SimpleDLLClass.cpp
#include "SimpleDLLClass.h"
SimpleDLLClass::SimpleDLLClass()
{
 m_nValue=0;
}
SimpleDLLClass::~SimpleDLLClass()
{
}