抽象基类实现接口一、    创建接口文件.h

#ifndef
_DBSERVER_INCLUDE
#define _DBSERVER_INCLUDE

typedef long HRESULT;

#define DEF_EXPORT _declspec(dllexport)

class IDB
{
   
//Inte***ces
public:
    //Inte***ce for data access
    virtual
HRESULT Read(short nTable,short nRow,LPWSTR lpszData)=0;
    virtual HRESULT
Write(short nTable,short nRow,LPCWSTR lpszData)=0;
    //Inte***ce for
database management
    virtual HRESULT Create(short &nTable,LPCWSTR
lpszName)=0;
    virtual HRESULT Delete(short nTable)=0;
    //Inte***ce
for database information
    virtual HRESULT GetNumTables(short
&nNumTables)=0;
    virtual HRESULT GetTableName(short nTable,LPWSTR
lpszName)=0;
    virtual HRESULT GetNumRows(short nTable,short
&nRows)=0;
    virtual ULONG Release()=0;
};

class
IDBSrvFactory
{
    //Inte***ce
public:
    virtual HRESULT
CreateDB(IDB** ppObject)=0;
    virtual ULONG Release()=0;
};


HRESULT DEF_EXPORT DllGetClassFactoryObject(IDBSrvFactory** ppObject);

#endif

二、    建立对象程序的头文件.h
并进行映射，函数声明顺序和参数跟接口文件一致

#ifndef
_DBSERVERIMP_INCLUDE
#define _DBSERVERIMP_INCLUDE
#include
"..\Inte***ce\DBsrv.h"

typedef long HRESULT;
//#define DEF_EXPORT
_declspec(dllexport)

class CDB:public IDB
{
    //Inte***ces

public:
    //Inte***ce for data access
    HRESULT DEF_EXPORT
Read(short nTable,short nRow,LPWSTR lpszData);
HRESULT DEF_EXPORT Write(short nTable,short nRow,LPCWSTR lpszData);
    //Inte***ce for
database management
    HRESULT DEF_EXPORT Create(short &nTable,LPCWSTR
lpszName);
    HRESULT DEF_EXPORT Delete(short nTable);
    //Inte***ce
for database information
    HRESULT DEF_EXPORT GetNumTables(short
&nNumTables);
    HRESULT DEF_EXPORT GetTableName(short nTable,LPWSTR
lpszName);
    HRESULT DEF_EXPORT GetNumRows(short nTable,short &nRows);

    ULONG DEF_EXPORT Release();
    //Implementation
private:
  
  CPtrArray m_arrTables;//Array of pointers to CStringArray(the "database")
 
   CStringArray m_arrNames;//Array of table names
public:
    ~CDB();

};

class CDBSrvFactory:public IDBSrvFactory
{
   
//Inte***ce
public:
    HRESULT DEF_EXPORT CreateDB(IDB** ppObject);

    ULONG DEF_EXPORT Release();
};

HRESULT DEF_EXPORT
DllGetClassFactoryObject(CDBSrvFactory** ppObject);
#endif

三、   
建立对象的实现文件
参数保持一致

HRESULT CDBSrvFactory::CreateDB(IDB** ppObject)

{
    *ppObject=(IDB*)new CDB;
    return NO_ERROR;
}

HRESULT DEF_EXPORT DllGetClassFactoryObject(IDBSrvFactory** ppObject)
{

    *ppObject=(IDBSrvFactory*)new CDBSrvFactory;
    return NO_ERROR;

}
from:
http://www.cppblog.com/kenbardy/archive/2006/03/14/4146.html(苍羽的学习库)