Help required with ZKTECO PullSDK "plcommpro.dll"

int ret = 0;
string str = string.Empty;
int BUFFERSIZE = 10 * 1024 * 1024;
byte[] buffer = new byte[BUFFERSIZE];
string deviTablename = string.Empty;
if (string.IsNullOrEmpty(filter))
{
    deviTablename = devtable;
}
else
{
     deviTablename = "user";;
}
str = string.Empty;
string devdatfilter = string.Empty;
if (!string.IsNullOrEmpty(filter))
{
    devdatfilter = string.Format("{0}={1}", "Pin", filter);
}
string options = "";
if (handle != IntPtr.Zero)
{
      ret = GetDeviceData(handle, ref buffer[0], BUFFERSIZE, deviTablename, str, devdatfilter, options);
      if (ret > 0)
      {
            var outstring = Encoding.Default.GetString(buffer).Replace("\0", string.Empty);
            string result = Regex.Replace(outstring, @"\r\n?|\n", "");
     
     return result;
     }         
}
return ret.ToString();