How to parse combined byteArray data in TCP Socket Server

I am using a socket client to send data to a socketServer :

At socket Client :

   string  strUser = "[Photo][User] + "\n"   ;    where \n  is  LF (Line feed) is the seperator

  byte[] Ar_user =  Encoding.UTF8.GetBytes(strUser)

  byte[]  Ar_TTL =  Ar_user +  PhotoByte[]  ( where PhotoByte[] is the actual photo)

 using this method to combine array :

    byte[] rv = new byte[ a1.Length + a2.Length + a3.Length ];
    System.Buffer.BlockCopy( a1, 0, rv, 0, a1.Length );
    System.Buffer.BlockCopy( a2, 0, rv, a1.Length, a2.Length );
    System.Buffer.BlockCopy( a3, 0, rv, a1.Length + a2.Length, a3.Length );

suppose the Ar_TTL is sent by a Socket client to a socket Server.

At socket server, the problem I want to solve:

1) Is above combine array workable ?

2) can I use this (\n) line feed inside this Ar_TTL ? will there be any of this in PhotoByte[]? what will be the best separator to use?

3) How to parse to get the [Photo][User]  and the actual PhotoByte[]  from Ar_TTL ? or is there other way to  do parsing?

This is what I used and not sure it is workable  :

             data = new byte[_client.ReceiveBufferSize];

            _client.GetStream().BeginRead(data, 0, System.Convert.ToInt32        (_client.ReceiveBufferSize),  ReceiveMessage, null);

     public void ReceiveMessage(IAsyncResult ar)
        {
                   int bytesRead;

                    const int LF = 10;
                     int i = 0;
                    int start = 0;
                     byte[]  receivePhoto;

                    while (data[i] != 0)
                    {
                        if (i + 1 > bytesRead)
                        {
                            break;
                        }
                        if (data[i] == LF)
                        {
                            //- How to parse and get the photoByte[] ?

                          }

                    }

     }

Thanks