获取文件数据流+叠加byte数组（给byte数组加包头包尾）

OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "(*.mp4)|*.mp4|(*.*)|*.*";
            ofd.RestoreDirectory = true;
            if (ofd.ShowDialog() == DialogResult.OK)
            {  
                try
                { // 打开文件 

                    FileStream fileStream = new FileStream(ofd.FileName, FileMode.Open, FileAccess.Read, FileShare.Read);

                    // 读取文件的 byte[] 
                     
                    byte[] brecord = new byte[fileStream.Length]; 
                    fileStream.Read(brecord, 0, brecord.Length); 
                    byte[] data1 = { 123, 66, 69, 83, 84, 69, 76 };
                    byte[] data2 = { 76, 69, 83, 84, 69, 76, 125 };

                    var data3 = new byte[data1.Length + data2.Length + brecord.Length];
                    Stream s = new MemoryStream();
                    s.Write(data1, 0, data1.Length);
                    s.Write(brecord, 0, brecord.Length);
                    s.Write(data2, 0, data2.Length);
                    s.Position = 0;
                    int r = s.Read(data3, 0, data3.Length);
                    if (r > 0)
                    {
                        //此时data3中就是合并的值了
                    }
                    mc.Send(data3);
                    
                    fileStream.Close();  
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message.ToString());
                }
                finally
                {
                    //sr.Close();
                    //fs.Close();
                }
            }