/// <summary>
       /// 
       /// </summary>
       /// <param name="key"></param>
       /// <param name="strValue"></param>
        public void Modify(string key, string strValue)                                                                                         //两个参数：要修改的键值   和   要修改的新值；                               
        {
          string   flagstr = strValue;
            if (strValue == string.Empty)
            {
                MessageBox.Show("连接串不能为空！");
                return;
            }
            //string XPath = "/configuration/userInfo/add[@key='?']";
            try
            {
                string XPath = "/configuration/appSettings/add[@key='?']";
                XmlDocument domWebConfig = new XmlDocument();

                //domWebConfig.Load((HttpContext.Current.Server.MapPath("web.config")));
                domWebConfig.Load(filepath);
                XmlNode addKey = domWebConfig.SelectSingleNode((XPath.Replace("?", key)));

                if (addKey == null)
                {
                    //Response.Write("<script>alert   (\"没有找到<add   key='" + key + "'   value=.../>的配置节\")</script>");
                    MessageBox.Show("没有找到<add   key='" + key + "'>的配置节");
                    return;
                }
                addKey.Attributes["value"].InnerText = strValue;
                domWebConfig.Save(filepath);
                MessageBox.Show("数据库连接配置成功","信息提示");
                            }
            catch
            {
            }

        }