ASP.NET

protected void Timer1_Tick(object sender, EventArgs e)
        {
            NameValueCollection MyImgList = new NameValueCollection();
            MyImgList.Add("Img1", "~/MyImages/Picture1.jpg");
            MyImgList.Add("Img2", "~/MyImages/Picture2.jpg");
            MyImgList.Add("Img3", "~/MyImages/Picture3.jpg");
            Random Rnd = new Random();
            int Indx = Rnd.Next(0, 4);
            //Image1.ImageUrl = MyImgList[Indx].ToString();
            // ********** Until here working fine...***************

            //Round Corner Image works...
            string path = Server.MapPath(MyImgList[Indx].ToString());
            int roundedDia = 50;
            using (System.Drawing.Image imgin = System.Drawing.Image.FromFile(path))
            {
                System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(imgin.Width, imgin.Height);
                Graphics g = Graphics.FromImage(bitmap);
                g.Clear(Color.White);
                Brush brush = new System.Drawing.TextureBrush(imgin);
                FillRoundedRectangle(g, new Rectangle(0, 0, imgin.Width, imgin.Height), roundedDia, brush);
                // done with drawing dispose graphics object.
                g.Dispose();
                // Stream Image to client.
                Response.Clear();
                Response.ContentType = "image/pjpeg";
                bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                Response.End();
                // dispose bitmap object.
                bitmap.Dispose();
            }

            Image1.ImageUrl = ?????? how to mention here ?
                              Because the confusion is image get disposed ????
        }