PInvoke和EntryPointNotFoundException

我无法理解下面的pinvoke有什么问题导致了EntryPointNotFoundException：

带有结构声明的C函数：

extern "C"__declspec (dllimport) __stdcall LONG NET_DVR_Login_V30 (char *sDVRIP, WORD wDVRPort, char *sUserName, char *sPassword, LPNET_DVR_DEVICEINFO_V30 lpDeviceInfo); typedef struct { BYTE sSerialNumber[48]; BYTE byAlarmInPortNum; BYTE byAlarmOutPortNum; BYTE byDiskNum; BYTE byDVRType; BYTE byChanNum; BYTE byStartChan; BYTE byAudioChanNum; BYTE byIPChanNum; BYTE byZeroChanNum; BYTE byMainProto; BYTE bySubProto; BYTE bySupport; BYTE byRes1[20]; }NET_DVR_DEVICEINFO_V30, *LPNET_DVR_DEVICEINFO_V30; 

C＃中的导入，结构声明和pinvoke：

  [DllImport("SDK.dll", SetLastError = true, CallingConvention = CallingConvention.StdCall)] public extern static int NET_DVR_Login_V30( [MarshalAs(UnmanagedType.LPStr)] string sDVRIP, ushort wDVRPort, [MarshalAs(UnmanagedType.LPStr)] string sUserName, [MarshalAs(UnmanagedType.LPStr)] string sPassword, ref NET_DVR_DEVICEINFO_V30 lpDeviceInfo); [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct NET_DVR_DEVICEINFO_V30 { [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 48)] public string sSerialNumber; public byte byAlarmOutPortNum; public byte byDiskNum; public byte byDVRType; public byte byChanNum; public byte byStartChan; public byte byAudioChanNum; public byte byIPChanNum; public byte byZeroChanNum; public byte byMainProto; public byte bySubProto; public byte bySupport; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)] public string byRes1; } NET_DVR_DEVICEINFO_V30 deviceInfo = new NET_DVR_DEVICEINFO_V30(); int result = Functions.NET_DVR_Login_V30(ip, port, user, password, ref deviceInfo); 

我通过dumpbin检查了函数名称，并没有被破坏。 所以我想知道为什么会发生EntryPointNotFoundException，如果参数有任何问题，例如，会发生PInvokeStackImbalance错误，比如说。 任何想法这个pinvoke可能有什么问题？