asp.net中下载功能

//流方式下载 
        protected void ButtonButtonDownload_Click(object sender, EventArgs e) 
        {
            //string fileName = "mychart.png";//客户端保存的文件名 
            //string filePath = Server.MapPath("/Report/mychart.png");//路径 
            ////以字符流的形式下载文件 
            //FileStream fs = new FileStream(filePath, FileMode.Open);
            //byte[] bytes = new byte[(int)fs.Length];
            //fs.Read(bytes, 0, bytes.Length);
            //fs.Close();
            //Response.ContentType = "application/octet-stream";
            ////通知浏览器下载文件而不是打开 
            //Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
            //Response.BinaryWrite(bytes);
            //Response.Flush();
            //Response.End(); 
            string path = Server.MapPath("/Report/mychart.png");//路径 
            if (File.Exists(path))
            {
                FileInfo DownloadFile = new FileInfo(path);
                Response.Clear();
                Response.ClearHeaders();
                Response.Buffer = false;
                Response.ContentType = "application/octet-stream";
                Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(DownloadFile.FullName, System.Text.Encoding.UTF8));
                Response.AppendHeader("Content-Length", DownloadFile.Length.ToString());
                Response.WriteFile(DownloadFile.FullName);
                Response.Flush();
                Response.End();
            }



            //Response.ContentType = "application/octet-stream";
            //Response.AddHeader("Content-Disposition", "attachment;filename=mychart.png");
            //string filename = Server.MapPath("/Report/mychart.png");
            ////指定编码 防止中文文件名乱码 
            //Response.HeaderEncoding = System.Text.Encoding.GetEncoding("gb2312");
            //Response.TransmitFile(filename); 
        }