string ReadBsonCstring()
        {
            using (MemoryStream memStream = new MemoryStream(128))
            {
                while (true)
                {
                    byte b = ReadByte();
                    if (b == 0x00)
                        break;
                    memStream.WriteByte(b);
                }
                return Encoding.UTF8.GetString(memStream.ToArray());
            }
        }