C#調用C++寫的DLL問題,急

Question

放到当前程序目录中，DLLIMPORT， 申明为外部函数，就可以调用了

Answer 1

public RTD_Program(int comPort,StringBuilder str)
        {
            _comPort = comPort;
            _strFile = new StringBuilder();
            _strFile = str;
            //_flashaddr = \Xff000;
        }
        //[DllImport("debugtools_library.dll", EntryPoint = "SetHDCP_CODE")]
        [DllImport("debugtools_library.dll")]
        private static extern long RtdProgram
            (
            int comport, 
            ref StringBuilder strFile, 
            UInt32 flashaddr, 
            int mode
            );
        //[DllImport("debugtools_library.dll", EntryPoint = "GetHDCP_CODE")]
        [DllImport("debugtools_library.dll")]
        private static extern long RtdRead
            (
            int comport,
            UInt32 flashaddr,
            UInt32 length,
            ref StringBuilder strFile //unsigned 
            );
        public long Write_HDCP()
        {
            retval = RtdProgram(_comPort, ref _strFile, 0xff000, 2);
            return retval;
        }
        public StringBuilder Read_HDCP()
        {
            RtdRead(_comPort, 0xff000, 320, ref _strBuff);
            return _strBuff;
        }
再執行public long Write_HDCP()的時候報錯
在DLL'debugtools_library.dll中找不到RtdProgram進入點
dll函數接口
__declspec(dllexport) long RtdProgram(int comport, char* strFile, UINT32 flashaddr, int mode);
__declspec(dllexport) long RtdRead(int comport, UINT32 flashaddr, UINT32 length, unsigned char* getData);