LPNET_DVR_FILECOND struFileCond = {0};
    struFileCond = (LPNET_DVR_FILECOND)malloc(sizeof(NET_DVR_FILECOND));
    memset(struFileCond,0x0,sizeof(NET_DVR_FILECOND));
    struFileCond->dwFileType = 0xFF;
    struFileCond->lChannel = 1;
    struFileCond->dwIsLocked  =0xFF;
    struFileCond->dwUseCardNo = 0;
    struFileCond->struStartTime.dwYear = 2017;
    struFileCond->struStartTime.dwMonth  = 5;
    struFileCond->struStartTime.dwDay    = 2;
    struFileCond->struStartTime.dwHour   = 2;
    struFileCond->struStartTime.dwMinute = 0;
    struFileCond->struStartTime.dwSecond = 0;
    struFileCond->struStopTime.dwYear    = 2017;
    struFileCond->struStopTime.dwMonth   = 5;
    struFileCond->struStopTime.dwDay     = 2;
    struFileCond->struStopTime.dwHour    = 11;
    struFileCond->struStopTime.dwMinute  = 7;
    struFileCond->struStopTime.dwSecond  = 0;

    LONG lFindHandle = NET_DVR_FindFile_V30(lUserID, struFileCond);

    if(lFindHandle < 0)
    {
        printf("find file fail ,last error %d\n", NET_DVR_GetLastError());

    }
    else
    {
    printf("Success!!!\n");
    }

public class HCNetSDK
{
      private const string origDllName = @"C:\docs\HCNetSDK.dll";

      #region structs
  [StructLayout(LayoutKind.Sequential)]
      public struct NET_DVR_DEVICEINFO_V30
      {
            public Byte[]   sSerialNumber;//[48];
    public Byte     byAlarmInPortNum;
    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;
    public Byte     bySupport1;
    public Byte     bySupport2;
    public UInt16   wDevType;
    public Byte     bySupport3;
    public Byte     byMultiStreamProto;
    public Byte     byStartDChan;
    public Byte     byStartDTalkChan;
    public Byte     byHighDChanNum;
    public Byte     bySupport4;
    public Byte     byVoiceInChanNum;
    public Byte     byStartVoiceInChanNo;
    public Byte     bySupport5;
    public Byte     bySupport6;
    public Byte     byMirrorChanNum;
    public UInt16   wStartMirrorChanNo;
    public Byte     bySupport7;
    public Byte     byRes2;
      }
      #endregion

      [DllImport(origDllName)]
      public static extern Boolean NET_DVR_Init();

      [DllImport(origDllName)]
      public static extern Boolean NET_DVR_SetConnectTime(UInt32 dwWaitTime, UInt32 dwTryTimes);

      [DllImport(origDllName)]
      public static extern Boolean NET_DVR_SetReconnect(UInt32 dwInterval, Boolean bEnableRecon);

      [DllImport(origDllName)]
      public static extern Int32 NET_DVR_Login_V30(string sDVRIP, UInt16 wDVRPort, string sUserName, string sPassword, ref NET_DVR_DEVICEINFO_V30 DeviceInfo);    

  [DllImport(origDllName)]
      public static extern UInt32 NET_DVR_GetLastError();    [DllImport(origDllName)]    public static extern Boolean NET_DVR_Cleanup();
}

static void Main(string[] args)    {
          Camera.HCNetSDK.NET_DVR_Init();
  Camera.HCNetSDK.NET_DVR_SetConnectTime(2000, 1);
  Camera.HCNetSDK.NET_DVR_SetReconnect(10000, true);

  Int32 lUserID;
  Camera.HCNetSDK.NET_DVR_DEVICEINFO_V30 struDeviceInfoV30 = new Camera.HCNetSDK.NET_DVR_DEVICEINFO_V30();
          lUserID = Camera.HCNetSDK.NET_DVR_Login_V30("ip", 8000, "login", "pass", ref struDeviceInfoV30);

  if (lUserID < 0)
  {
    Console.WriteLine("Login failed, error code: {0}\n", Camera.HCNetSDK.NET_DVR_GetLastError());
    Camera.HCNetSDK.NET_DVR_Cleanup();
    Console.ReadKey();
    return;
  }
          
  Console.WriteLine("The max number of analog channels: {0}\n", struDeviceInfoV30.byChanNum);
          Console.WriteLine("The max number of IP channels: {0}\n", struDeviceInfoV30.byIPChanNum + struDeviceInfoV30.byHighDChanNum * 256); 
  Console.WriteLine("Done!");
          Console.ReadKey();
    }

[DllImport(origDllName, CharSet = CharSet.Unicode)]
        public static extern Int32 NET_DVR_Login_V30(string sDVRIP, UInt16 wDVRPort, string sUserName, string sPassword, ref NET_DVR_DEVICEINFO_V30 DeviceInfo);

[DllImport(origDllName, CharSet = CharSet.Ansi)]
        public static extern Int32 NET_DVR_Login_V30(char[] sDVRIP, UInt16 wDVRPort, char[] sUserName, char[] sPassword, ref NET_DVR_DEVICEINFO_V30 DeviceInfo);