C++ 接口:

BOOL CLIENT_QueryDevState(LLONG lLoginID, int nType, char *pBuf, int nBufLen, int *pRetLen, int waittime=1000);

C++ struct 1:

struct NET_PTZ_PRESET_LIST
{  
  DWORD                                   dwSize;
  DWORD                                   dwMaxPresetNum;
  DWORD                                   dwRetPresetNum;
  NET_PTZ_PRESET                          *pstuPtzPorsetList;
};

C++ struct 2:

struct NET_PTZ_PRESET
{
  int                                     nIndex;
  char                                    szName[PTZ_PRESET_NAME_LEN];
  char                                    szReserve[64];
};

我申明的接口:

[DllImport(GlobalConst.DHNETSDK_PATH, CallingConvention = CallingConvention.Cdecl)]
public static extern bool CLIENT_QueryDevState(long lLoginID, int nType, IntPtr pBuf, int nBufLen, ref int pRetLen, int waittime = 1000);

我申明的结构体 1:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct NET_PTZ_PRESET_LIST
{
   public int dwSize;
   public int dwMaxPresetNum;
   public int dwRetPresetNum;
   [MarshalAs(UnmanagedType.ByValArray)]
   public NET_PTZ_PRESET[] pstuPtzPorsetList;
}

我申明的结构体 2:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct NET_PTZ_PRESET
{
   public int nIndex;
   [MarshalAs(UnmanagedType.ByValTStr, SizeConst = GlobalConst.PTZ_PRESET_NAME_LEN)]
   public string szName;
   [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
   public string szReserve;
}

我的调用:

int nType = GlobalConst.DH_DEVSTATE_PTZ_PRESET_LIST;
int pRetLen = 0;
int sizeList = Marshal.SizeOf(typeof(GlobalStruct.NET_PTZ_PRESET_LIST));
int bufSize = sizeList;
var pBuf = Marshal.AllocHGlobal(bufSize);
Marshal.StructureToPtr(nET_PTZ_PRESET_LIST, pBuf, true);

var result = DHSDK.CLIENT_QueryDevState(_loginID, nType, pBuf, bufSize, ref pRetLen, 3000);
if (!result)
{
    Marshal.FreeHGlobal(pBuf);
    var errorCode = GetLastError();
    return;
}

var obj = (GlobalStruct.NET_PTZ_PRESET_LIST)Marshal.PtrToStructure(pBuf, 
    typeof(GlobalStruct.NET_PTZ_PRESET_LIST));

结果：要么接口直接报内存错误；要么接口调用失败，返回的error=7（用户参数不合法）；要么回来的数据转成结构体后，里面的数据有问题。

请教下各位这个接口到底该怎么正确调用？