转载：轻量级Config文件AppSettings节点编辑帮助类

using System.Configuration;
using System.Windows.Forms;

namespace Allyn.Common
{
    public class XmlHeper
    {
        ///<summary> 
        ///返回Config文件中appSettings配置节的value项  
        ///</summary> 
        ///<param name="strKey">节点Key</param> 
        ///<returns>值</returns> 
        public static string GetAppConfig(string strKey)
        {
            string file = Application.ExecutablePath;
            Configuration config = ConfigurationManager.OpenExeConfiguration(file);

            foreach (string key in config.AppSettings.Settings.AllKeys)
            {
                if (key == strKey)
                {
                    return config.AppSettings.Settings[strKey].Value.ToString();
                }
            }
            return string.Empty;
        }

        ///<summary>  
        ///在Config文件中appSettings配置节增加一对键值对  
        ///</summary>  
        ///<param name="newKey">节点名称</param>  
        ///<param name="newValue">信值</param>  
        public static void UpdateAppConfig(string newKey, string newValue)
        {
            string file = System.Windows.Forms.Application.ExecutablePath;
            Configuration config = ConfigurationManager.OpenExeConfiguration(file);

            bool exist = false;

            foreach (string key in config.AppSettings.Settings.AllKeys)
            {
                if (key == newKey) {  exist = true; }
            }

            if (exist)  { config.AppSettings.Settings.Remove(newKey); }

            config.AppSettings.Settings.Add(newKey, newValue);
            config.Save(ConfigurationSaveMode.Modified);

            ConfigurationManager.RefreshSection("appSettings");
        }
    }
}

转载：https://www.cnblogs.com/allyn/p/10178067.html