FileInfo fileInfo = new FileInfo(filePath);
                Response.Clear();
                Response.ClearContent();
                Response.ClearHeaders();
                Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
                Response.AddHeader("Content-Length", fileInfo.Length.ToString());
                Response.AddHeader("Content-Transfer-Encoding", "binary");
                Response.ContentType = "application/octet-stream";
                Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
                Response.WriteFile(fileInfo.FullName);
                Response.Flush();
                Response.End();
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message);
            }

            /*************以下為流方式下載****************/
            //string fileName = "aaa.txt";//客戶端保存的文件名
            //string filePath = Server.MapPath("DownLoad/aaa.txt");//路徑

            ////以字符流的形式下載文件
            //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";
            ////通知瀏覽器下載文件而不是打開(kāi)
            //Response.AddHeader("Content-Disposition", "attachment;  filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
            //Response.BinaryWrite(bytes);
            //Response.Flush();
            //Response.End();

        }