string mac = "";
             try
            {
                mac = (context.Request["mac"]);
                mac = mac.Replace("-", "");
             }
            catch {
                    Bitmap bitmap =  null;
                    byte[] cachedData = null;
                    if (bitmap != null)
                    {
                        MemoryStream stream = new MemoryStream();
                        bitmap.Save(stream, ImageFormat.Png);
 
                        cachedData = stream.ToArray();
                        context.Cache.Insert(kehuKey, cachedData, null, DateTime.Now.AddSeconds(60), Cache.NoSlidingExpiration);
                        context.Response.ContentType = "image/jpeg";
                        context.Response.OutputStream.Write(cachedData, 0, cachedData.Length);
                }
            }