打开函数时出错

////fzyktclient.dll 中的ykt_readopencardno_local函数及参数无误， 行158出错 提示THIS指针为空 ， 帮助看看是哪出错了
#include<windows.h>
#include<stdlib.h>
#include<string.h>
#include<iostream.h>
#include<stdio.h>
//#include<ClassHeader.h>///接口类
///接口类定义
class IckJk {
public:
    IckJk ();  //默认构造函数
    ~IckJk ();  //析构函数
    void ykt_open (void);//初始化
    void ykt_ReadNo(void);  //
    void ykt_close(void); //关闭
    void ykt_readinfo(void);
    void temp1(void);
    int read_YesOrNo() const;
    char read_pCardno() ;
private:
//    HINSTANCE hinstance;//DLL句柄
    char *test;
    int YesOrNo; //函数调用时是否成功
    int nDeviceType; //设备类型(10或12)
    int nCom; //端口（0-9） 0 - com1 1 - com2 … 9 - usb
    int nBaud;//波特率（1-4） 1 - 9600   2 - 19200   3 - 28800  4 - 57600  建议用3或者2
    char *pRegion;//地区编号 3500代表省本级 Char(4)
    char *pWarnmsg;//警告信息 Char(1024)
    char *pErrmsg;//错误信息 Char(1024)

    char *pDeptID;//网点编号
    char *pDeptKey;//  网点密钥
    char *pCardtype;//  
    char *pCardno;//   

    char *pIssuedeptid;//
    char *pIssuedate;//  
    char *pIdtype;//  
    char *pId;//  
    char *pName;//
    char *pSex;//
    char *pBirthDate;//  
    char *pCompany;//  
    char *pAddress;//  
    char *pTelephone;//

    int offset;//
    int length;//
    char *pData;//
};


//稳定初始状态
IckJk::IckJk ()
    {
    nDeviceType = 12;  //设备类型(10或12)
    nCom = 0;  //端口（0-9） 0 - com1 1 - com2 … 9 - usb
    nBaud = 2; //波特率（1-4） 1 - 9600   2 - 19200   3 - 28800  4 - 57600  建议用3或者2
    pRegion = "3508" ;//地区编号 3500代表省本级 Char(4)
    pWarnmsg="-warn-";
    pErrmsg="-err-";

    pDeptID= "0104" ;
    pDeptKey= "" ; //  
    pCardtype="F";
    pCardno = "-card-";

    offset = 0;//
    length= 8 ;//
    pData="8";//

    YesOrNo=9;
    test= " -test- " ;//
}
//析构函数
IckJk::~IckJk (){
}

void IckJk::temp1()
{     
    cout<<"YesOrNo "<<YesOrNo ;
    cout<<"pWarnmsg "<<pWarnmsg ;
    cout<<"pErrmsg "<<pErrmsg ;
    cout<<"pCardno "<<pCardno ;
}
int IckJk::read_YesOrNo() const
{     
    return YesOrNo;
}

char IckJk::read_pCardno(void)
{     
    return (*pCardno);
}


extern "C" __declspec(dllimport) int ykt_opendevice(int ,int ,int ,char *,char *,char *);
void IckJk::ykt_open(void)  //初始化
{
//
typedef int(WINAPI *ykt_opendevice)(int nDeviceType,int nCom,int nBaud,LPCTSTR str ,char *pWarnmsg,char *pErrmsg);
//---定义
HINSTANCE hinstance;//DLL句柄  
hinstance=LoadLibrary("fzyktclient.dll");
cout<<hinstance;
if(hinstance)
{
ykt_opendevice funopendevice=NULL;
funopendevice=(ykt_opendevice)GetProcAddress(hinstance,"ykt_opendevice");
//            //GetProcAddress得到了所加载DLL模块中函数ykt_opendevice的地址并赋给了funopendevice
if(funopendevice)
    {
         cout<<funopendevice;
        YesOrNo=1;
             YesOrNo=funopendevice(nDeviceType,nCom,nBaud,pRegion,pWarnmsg,pErrmsg);
             cout<<YesOrNo;
            if (YesOrNo != 0)
            { if (pWarnmsg == NULL)
                    {IckJk::pWarnmsg = "警告：请先正确设置串口！";}
                else
                    {IckJk::pWarnmsg = pWarnmsg ;}
              if (pErrmsg == NULL)
                    {IckJk::pErrmsg = "错误：打开失败！";}
                else
                    {IckJk::pErrmsg = pErrmsg ;}

            }   
                else
            {
                cout<<"打开成功";
                cout<<YesOrNo;
            }
    }  //if(funopendevice)
}  //if(hinstance)
     FreeLibrary(hinstance);//卸载fzyktclient.dll文件；
}


extern "C" __declspec(dllimport) int readno_local(LPCTSTR , char *,char *, char * ,char * , char *,char *);
void IckJk::ykt_ReadNo(void) //脱机读取卡号
{
//
typedef int(WINAPI *readno_local)(LPCTSTR str, char *pDeptID,char *pDeptKey, char *pCardtype,char *pCardno, char *pWarnmsg,char *pErrmsg);
//---定义
HINSTANCE hinstance;//DLL句柄  
hinstance=LoadLibrary("fzyktclient.dll");
cout<<hinstance;
if(hinstance)
{
readno_local funreadno_local=NULL;
funreadno_local=(readno_local)GetProcAddress(hinstance,"ykt_readopencardno_local");
//            //GetProcAddress得到了所加载DLL模块中函数ykt_opendevice的地址并赋给了funopendevice
if(funreadno_local)
    {
         cout<<funreadno_local;
        YesOrNo=2;
        //下一行出错  测试时提示内存为空， 函数参数无误
        YesOrNo=funreadno_local(pRegion,pDeptID,pDeptKey,pCardtype,pCardno,pWarnmsg,pErrmsg);
             cout<<YesOrNo;
            if (YesOrNo != 0)
            {
                IckJk::pWarnmsg = pWarnmsg;
                IckJk::pErrmsg = pErrmsg;
            }   
                else
            {
                cout<<"读卡号成功";
                cout<<YesOrNo;
            }
    }  //if(funopendevice)
}  //if(hinstance)
     FreeLibrary(hinstance);
}

//extern "C" __declspec(dllimport) int ykt_readopencardno_local(char *, char *,char *, char * ,char * , char *,char *);
extern "C" __declspec(dllimport) int ykt_readopencardinfo_local(char *, char *,char *, char *,char *, char *,char *,char *,char *,char *, char *,char *,char *,char *,char *, char *,char *);
extern "C" __declspec(dllimport) int ykt_closedevice(char *, char *);
void main(void)
{
    IckJk t;
    t.ykt_open();
    if (! t.read_YesOrNo())
        {
            cout<<"a";
            t.ykt_ReadNo();
        }
    //    t.ykt_readinfo ();
                if (! t.read_YesOrNo())
                    {
                        cout<<"b";}
        
    //    t.ykt_close();
                if (! t.read_YesOrNo())
                {cout<<"c";    }
        t.temp1();

 }