使用文件流下载附件

id = Request.QueryString["id"];
            Model.TEACHINGACRESO _mAttachment = new Bll.TEACHINGACRESO().GetModel(id);
            string basePath = Hzjg.Common.Config.ConfigManage.fGetAppConfig("SaveFilePath");
            string fileurl = basePath + _mAttachment.SAVEADDRESS.Replace("/", "\");

            if (File.Exists(fileurl))
            {
                string filename = _mAttachment.NAME;
                HttpContext.Current.Response.Clear();
                HttpContext.Current.Response.ClearContent();
                HttpContext.Current.Response.ClearHeaders();
                HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename));
                HttpContext.Current.Response.WriteFile(string.Format("{0}\{1}", basePath, _mAttachment.SAVEADDRESS.Replace("/", "\")));
                HttpContext.Current.Response.Flush();
                HttpContext.Current.Response.End();
            }
            else
            {
                Hzjg.Common.Utility.Log.fWriterLog("下载失败，请检查文件是否存在");
                Response.Write("<script language='javascript'>alert("下载失败，请检查文件是否存在");location='FileAndFolder.aspx?group=" + Request.QueryString["group"] + "';</script>");
            }