如何通过webSocket发送PictureBox图像

我需要一些帮助这段代码。我正在捕获桌面屏幕并在PictureBox中显示它，这很好，但我正试图将该PictureBox图像转换为字节[]，然后转换为字符串，这样我就可以通过WebSocket (ws)发送它。

1)。我的第一个问题是，用图像绘制的PictureBox不会转换成字节[]或二进制，我在那里做错了什么?还有别的办法吗?

2)。第二个问题是，我需要将这些byte[]转换为字符串这样我就可以将它们与其他字符串一起发送，在接收应用程序中，我将使用分隔符分割字符串，然后将字符串转换为byte[]然后转换为picturebox

WebSocket ws;
// Here goes the rest of the websocket code, which it works just fine.
private void Display(Bitmap desktop)
{
    Graphics g;
    Rectangle r;
    if (desktop != null)
    {
        // Here I'm capturing the desktop screen and filling the PictureBox1 with it.
        r = new Rectangle(0, 0, PictureBox1.Width, PictureBox1.Height);
        g = PictureBox1.CreateGraphics();
        g.DrawImage(desktop, r);
        g.Flush();
        // Here I'm trying to convert the filled PictureBox into Byte[]
        ImageConverter converter = new ImageConverter();
        byte[] imageBytes = (byte[])converter.ConvertTo(PictureBox1.Image, typeof(byte[]));
        // Here I'm trying to conver the byte[] into a string text
        string bytesString1 = System.Text.Encoding.ASCII.GetString(imageBytes);
        string firstString = "1504";
        string separator = "+";
        // Here I'm sending the message via Websocket, which includes the "firstString",
        // the "separator" so then we can use Split in the receiving application, and 
        // then the "bytesString1" which contains the image data.
        string messageToSend = firstString + separator + bytesString1;
        ws.Send(messageToSend);
    }
}

请帮忙!