How to convert webcam captured picture to byte

You can use Image.Save method which receives stream. Try this piece of code:

Image img = new Bitmap(10, 10);
byte[] binaryImage = null;

using (System.IO.MemoryStream memStream = new System.IO.MemoryStream())
{
    img.Save(memStream, ImageFormat.Jpeg);
    memStream.Flush();

    binaryImage = new byte[memStream.Position];
    memStream.Position = 0;

    memStream.Read(binaryImage, 0, binaryImage.Length);

}

I've just written it from scratch without testing, but I'm sure that you'll test it :)

Zoran