视频会议应用。尝试许多解决方案后，NullReferenceException未被删除

Question

我正在尝试使用Visual C＃开发视频会议应用。这是Start_Sending_Video_Conference的一大块：

    private void Start_Sending_Video_Conference(string remote_IP,int port_number)
    {
        try
        {
            using ( ms = new MemoryStream())
            {
                //ms = new MemoryStream();// Store it in Binary Array as Stream
                pictureBox1.Image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                byte[] arrImage = ms.GetBuffer();//returns the array of unsigned bytes
                myclient = new TcpClient(remote_IP, port_number);//Connecting with server
                myns = myclient.GetStream();//returns the stream 
                mysw = new BinaryWriter(myns);//encoding
                mysw.Write(arrImage);//send the stream to above address
                ms.Flush();
                mysw.Flush();
                myns.Flush();
                ms.Close();
                mysw.Close();
                myns.Close();
                myclient.Close();
            }
        }

         catch (Exception ex)
        {

            Capturing.Enabled = false;
            MessageBox.Show(ex.Message,"Video Conference Error Message",MessageBoxButtons.OK,MessageBoxIcon.Error);

        }

    }

我得到了

  

PictureBox1.Image.Save上的NullReferenceException（ms，   System.Drawing.Imaging.ImageFormat.Jpeg）;方法和参数   功能全部定义。 'ms'已使用'new'定义   可以看到关键字。

所有方法都定义了参考文献。我错过了什么？我该怎么解决这个问题？