If you want to do what I think, give this a try:
Response.Clear();
Response.ContentType = "image/bmp";
byte[] im = (byte[])dt.Rows[0]["Photo"];
bm Image = new Bitmap(new MemoryStream(im));
bm.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Bmp)
Be careful about cleaning up your memory.