C# Web.config 配置文件读取、设置

using System;
using System.Configuration;

namespace ConfigurationTool
{
    /// <summary>
    /// 用于XML操作
    /// </summary>
    public class ConfigurationHelper
    {
        //定义一个用于保存静态变量的实例
        private static ConfigurationHelper instance = null;
        //定义一个保证线程同步的标识
        private static readonly object locker = new object();
        //构造函数为私有，使外界不能创建该类的实例
        private ConfigurationHelper() { }
        public static ConfigurationHelper Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (locker)
                    {
                        if (instance == null) instance = new ConfigurationHelper();
                    }
                }
                return instance;
            }
        }

        /// <summary>
        /// 读取指定路径下Web.config，指定key的value
        /// </summary>
        /// <param name="filePath">路径</param>
        /// <param name="key">key</param>
        /// <returns></returns>
        public string ReadConfiger(string filePath, string key)
        {
            ExeConfigurationFileMap map = new ExeConfigurationFileMap();
            map.ExeConfigFilename = filePath;
            Configuration config = ConfigurationManager.OpenMappedExeConfiguration(map, ConfigurationUserLevel.None);
            string value = config.AppSettings.Settings[key].Value;
            return value;
        }

        /// <summary>
        /// 保存指定路径下Web.config，指定key的value
        /// </summary>
        /// <param name="filePath">路径</param>
        /// <param name="key">key</param>
        /// <param name="value">value</param>
        /// <returns></returns>
        public string SaveConfiger(string filePath, string key,string value)
        {
            ExeConfigurationFileMap map = new ExeConfigurationFileMap();
            map.ExeConfigFilename = filePath;
            Configuration config = ConfigurationManager.OpenMappedExeConfiguration(map, ConfigurationUserLevel.None);
            //写入<add>元素的Value
            config.AppSettings.Settings[key].Value = value;
            //一定要记得保存，写不带参数的config.Save()也可以
            config.Save();
            //刷新，否则程序读取的还是之前的值（可能已装入内存）
            ConfigurationManager.RefreshSection("appSettings");

            return value;
        }

        /// <summary>
        /// 根据key获取value
        /// </summary>
        /// <param name="key">key</param>
        /// <returns></returns>
        public string GetValueByKey(string key)
        {
            try
            {
                return ConfigurationManager.AppSettings[key];
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
        }

        /// <summary>
        /// 设置key对应value
        /// </summary>
        /// <param name="key">key</param>
        /// <param name="value">value</param>
        public void SetValueByKey(string key, string value)
        {
            try
            {
                //获取Configuration对象
                Configuration config = System.Configuration.ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                //根据Key读取<add>元素的Value
                //string name = config.AppSettings.Settings[key].Value;
                //写入<add>元素的Value
                config.AppSettings.Settings[key].Value = value;
                //增加<add>元素
                //config.AppSettings.Settings.Add("url", "//www.jb51.net");
                //删除<add>元素
                //config.AppSettings.Settings.Remove("name");
                //一定要记得保存，写不带参数的config.Save()也可以
                config.Save();
                //刷新，否则程序读取的还是之前的值（可能已装入内存）
                ConfigurationManager.RefreshSection("appSettings");
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
        }

    }
}