System.IO.MemoryStream ms = new System.IO.MemoryStream();
System.IO.Stream str = new FileUpload().PostedFile.InputStream;
System.Drawing.Bitmap map = new System.Drawing.Bitmap(str);
map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/gif";
Response.BinaryWrite(ms.ToArray());

System.IO.FileStream fs = new System.IO.FileStream("Filename", System.IO.FileMode.Open, System.IO.FileAccess.Read);
byte[] datas = new byte[fs.Length];
fs.Read(datas, 0, Convert.ToInt32(fs.Length));
fs.Close();
Response.OutputStream.Write(datas,0,Convert.ToInt32(fs.Length));
Response.End();