说明ms有问题，首先确保有读到数据，这种情况是保存到库的时候出错的。
原来你可能是这样写的：
MemoryStream stream = new MemoryStream();
PictureBox1.Image.Save(stream, ImageFormat.Bmp ); //这里出错，原图片格式是JPEG
byte [] bytestream = new byte [ stream.Length ];
stream .Read (bytestream ,0,bytestream .Length );
stream.Flush();
应该为：
MemoryStream stream = new MemoryStream();
PictureBox1.Image.Save(stream,PictureBox1 .Image .RawFormat );
byte[] bytestream = stream.ToArray();
stream.Flush();