C# 读取配置指定Config文件--亲测通过

 public class ConfigUtils
    {
        public static String GetKey(String configPath,String key)
        {
            Configuration ConfigurationInstance = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap()
            {
                ExeConfigFilename = configPath
            }, ConfigurationUserLevel.None);


            if (ConfigurationInstance.AppSettings.Settings[key] != null)
                return ConfigurationInstance.AppSettings.Settings[key].Value;
            else

                return string.Empty;
        }

        public static bool SetKey(String configPath, String key,String vls)
        {
            try
            {
                Configuration ConfigurationInstance = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap()
                {
                    ExeConfigFilename = configPath
                }, ConfigurationUserLevel.None);

                if (ConfigurationInstance.AppSettings.Settings[key] != null)
                    ConfigurationInstance.AppSettings.Settings[key].Value = vls;
                else
                    ConfigurationInstance.AppSettings.Settings.Add(key, vls);
                ConfigurationInstance.Save(ConfigurationSaveMode.Modified);
                ConfigurationManager.RefreshSection("appSettings");
                return true;
            }
            catch
            {
                return false;
            }
        }
    }

   public static bool SetXXXKey(String vls)
        {
            return ConfigUtils.SetKey(AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "XXX.exe.config", "XXX",vls);
        }

//XXX分别是文件名/Key名

        public static String GetXXXKey()
        {
            return ConfigUtils.GetKey(AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "XXX.exe.config", "XXX");
        }

//XXX分别是文件名/Key名