/// <summary>   

        /// 上传文件
        /// </summary>
        /// <param name="pf">HttpPostedFile</param>
        /// <param name="path">路径</param>
        /// <param name="filename">输出文件名</param>
        /// <returns>错误信息</returns>
        public static string UploadFile(HttpPostedFile pf,string savepath, out string filename)
        {
            string fileExt = GetFileExt(pf.FileName);
            if (!AllowFileExt(fileExt))
            {
                filename = string.Empty;
                return "上传文件扩展名不被允许";
            }
            else if (pf.ContentLength >1048576)
            {
                filename = string.Empty;
                return "上传文件大小不得超过1MB";
            }

            filename = GetNewFileName() + "." + fileExt;
            string path = HttpContext.Current.Server.MapPath("~" + "/" + savepath + "/" + filename);
            pf.SaveAs(path);
            return string.Empty;
        }

        /// <summary>
        /// 新文件名
        /// </summary>
        /// <returns></returns>
        public static string GetNewFileName()
        {
            return DateTime.Now.ToString("MMddhhmmss");
        }

        /// <summary>
        /// 取得文件扩展名
        /// </summary>
        /// <param name="filename">文件名</param>
        /// <returns>扩展名字符串</returns>
        static public string GetFileExt(string filename)
        {
            int pos = filename.LastIndexOf(".");
            return filename.Substring(pos + 1);
        }

        /// <summary>
        /// 取得文件名
        /// </summary>
        /// <param name="filename"></param>
        /// <returns>主文件名字符串</returns>
        static public string GetFileName(string filename)
        {
            int pos = filename.LastIndexOfAny(new char[] { '\\', '/' });
            int pos1 = 0;
            int len = pos - pos1;
            return filename.Substring(pos1 + 1, len);
        }
        /// <summary>
        /// 允许上传的文件类型
        /// </summary>
        /// <param name="ext">文件类型</param>
        /// <returns>是/否</returns>
        static public bool AllowFileExt(string ext)
        {
            try
            {
                string ex = "txt,xls,doc,docx,rar,zip";
                foreach (string s in ex.Split(','))
                {
                    if (ext.ToLower() == s.ToLower())
                    {
                        return true;
                    }
                }
            }
            catch { return true; }
            return false;
        }

 <asp:FileUpload ID="FileUpload1" runat="server" CssClass="fileupload" />

//上传文件加入数据库

 protected void Button1_Click(object sender, EventArgs e)
{
        string filename = "";
        string msg = Common .UploadFile(FileUpload1.PostedFile, "upload", out filename);
        if ("" == msg)
        {
            attendInfo.AttachUrl = filename;//成功
            return true;
        }
        else
        {
            Common.ShowMessage(""+msg+"");//失败
            return false;
        }