SQ12345_OutApi/SQ12345_OutA.../Helper/ConfigHelper...

using System;
using System.Configuration;
using System.IO;
using System.Web;
using System.Xml;
namespace SQ12345_OutApi.Utility
{
    public class ConfigHelper
    {
        static XmlDocument xDoc;
        static XmlNode xNode;

        static ConfigHelper()
        {
            lasttime = new FileInfo(path).LastWriteTime;
            xDoc = new XmlDocument();
            xDoc.Load(path);
            xNode = xDoc.SelectSingleNode("//appSettings");
        }

        static string path = HttpContext.Current.Server.MapPath("~/Configs/system.config");
        static DateTime lasttime = DateTime.Now;

        /// <summary>
        /// 根据Key取Value值
        /// </summary>
        /// <param name="key"></param>
        public static string GetValue(string key)
        {
            try
            {
                DateTime dt = new FileInfo(path).LastWriteTime;
                if (dt != lasttime)
                {
                    xDoc = new XmlDocument();
                    xDoc.Load(path);
                    xNode = xDoc.SelectSingleNode("//appSettings");
                    lasttime = dt;
                }
                var xElem1 = (XmlElement)xNode.SelectSingleNode("//add[@key='" + key + "']");
                return xElem1?.GetAttribute("value") ?? "";
            }
            catch
            {
                return "";
            }
        }
        /// <summary>
        /// 根据Key修改Value
        /// </summary>
        /// <param name="key">要修改的Key</param>
        /// <param name="value">要修改为的值</param>
        public static void SetValue(string key, string value)
        {
            try
            {
                DateTime dt = new FileInfo(path).LastWriteTime;
                if (dt != lasttime)
                {
                    xDoc = new XmlDocument();
                    xDoc.Load(path);
                    xNode = xDoc.SelectSingleNode("//appSettings");
                    lasttime = dt;
                }

                XmlElement xElem1;
                XmlElement xElem2;
                xElem1 = (XmlElement)xNode.SelectSingleNode("//add[@key='" + key + "']");
                if (xElem1 != null) xElem1.SetAttribute("value", value);
                else
                {
                    xElem2 = xDoc.CreateElement("add");
                    xElem2.SetAttribute("key", key);
                    xElem2.SetAttribute("value", value);
                    xNode.AppendChild(xElem2);
                }
                xDoc.Save(path);
            }
            catch
            { }
        }
    }
}