Question

C#调用DLL结构体时，出现尝试读取或写入受保护的内存。这通常指示其他内存已损坏!

C++代码
typedef struct tagIDCardData{
char Name[32]; //姓名
char Sex[6]; //性别
char Nation[20]; //名族
char Born[18]; //出生日期
char Address[72]; //住址
char IDCardNo[38]; //身份证号
char GrantDept[32]; //发证机关
char UserLifeBegin[18]; // 有效开始日期
char UserLifeEnd[18]; // 有效截止日期
char reserved[38]; // 保留
char PhotoFileName[255];// 照片路径
}IDCardData;
int _stdcall Syn_ReadMsg( int iPort,int iIfOpen,IDCardData *pIDCardData );

C#代码
[StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
public struct IDCardData
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string Name; //姓名
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string Sex; //性别
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]
public string Nation; //名族
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 18)]
public string Born; //出生日期
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 72)]
public string Address; //住址
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 38)]
public string IDCardNo; //身份证号
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string GrantDept; //发证机关
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 18)]
public string UserLifeBegin; // 有效开始日期
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 18)]
public string UserLifeEnd; // 有效截止日期
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 38)]
public string reserved; // 保留
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 255)]
public string PhotoFileName; // 照片路径
}

[DllImport("SynIDCardAPI.dll", EntryPoint = "Syn_ReadMsg", CharSet = CharSet.Ansi)]
public static extern int Syn_ReadMsg(int iPortID, int iIfOpen, ref IDCardData pIDCardData);

应用代码
public int nRet=0;
pulblic int nPort=1001;
private void ListenCard()
{
try
{
while (!_bListenCardQuit)
{
IDCardData CardMsg = new IDCardData();
nRet = Syn_ReadMsg(nPort, 0, ref CardMsg);//读取信息
GC.Collect(2, GCCollectionMode.Optimized);
Thread.Sleep(500);
}
_bQuitListenCardDone = true;

#region 异常
catch (Exception eE)
{
OLog.WriteLog(Log.MsgType.Error, eE.StackTrace, eE.Message);
}
#endregion
}
运行到这里（ nRet = Syn_ReadMsg(nPort, 0, ref CardMsg);//读取信息），第一次成功，运行第二次的时候就报错：出现尝试读取或写入受保护的内存。这通常指示其他内存已损坏!
恳请各位大牛帮忙解决一下问题啊！

Answer 1

[DllImport("SynIDCardAPI.dll", EntryPoint = "Syn_ReadMsg", CharSet = CharSet.Ansi)]
public static extern int Syn_ReadMsg(int iPortID, int iIfOpen, ref IDCardData pIDCardData);

你这样改下试试
[DllImport("SynIDCardAPI.dll", EntryPoint = "Syn_ReadMsg", CharSet = CharSet.Ansi)]
public static extern int Syn_ReadMsg(int iPortID, int iIfOpen, IDCardData[] pIDCardData);

调用时
IDCardData[] pIDCardData=new IDCardData[10];
传入 pIDCardData[0]

追问

Syn_ReadMsg(nPort, 0, pIDCardData[0]); 这里出错

追答

错了 你试试这样 (还是你原来的)
[DllImport("SynIDCardAPI.dll", EntryPoint = "Syn_ReadMsg", CharSet = CharSet.Ansi)]
public static extern int Syn_ReadMsg(int iPortID, int iIfOpen, ref IDCardData pIDCardData);

调用时
IDCardData[] pIDCardData=new IDCardData[10];
传入 pIDCardData[0]

Answer 2

这种提示一般是被读取的文件未释放而在此重读引起,检查看是否存在这样问题?