common/Ui/Common.UI/Infrastructure/Appsettings.cs

namespace Common.UI.Infrastructure
{
    using System;
    using System.Configuration;
    using System.Linq;

    public static class Appsettings
    {
        private static readonly string dll = typeof(Appsettings).Assembly.Location;

        public static string GetSetting(string settingKey)
        {
            var settingValue = default(string);

            try
            {
                var configuration = ConfigurationManager.OpenExeConfiguration(dll);
                var settings = configuration.AppSettings.Settings;

                settingValue = settings[settingKey]?.Value;
            }
            catch (Exception e)
            {
                AppHost.NLogger.Error(e);
            }

            return settingValue;
        }

        public static string SetSetting(string settingKey, string settingValue)
        {
            try
            {
                var configuration = ConfigurationManager.OpenExeConfiguration(dll);
                var settings = configuration.AppSettings.Settings;

                if (!settings.AllKeys.Any(x => x == settingKey))
                {
                    settings.Add(settingKey, string.Empty);
                }

                settings[settingKey].Value = settingValue;

                configuration.Save(ConfigurationSaveMode.Modified);
                ConfigurationManager.RefreshSection("appSettings");
            }
            catch (Exception e)
            {
                AppHost.NLogger.Error(e);
            }

            return settingValue;
        }
    }
}