AppConfigBase.cs

using System;
using System.ComponentModel;
using System.Reflection;
using System.Runtime.CompilerServices;
using Windows.ApplicationModel.Resources;
using Windows.Storage;

namespace App28
{
    public class AppConfigBase<Impl> : INotifyPropertyChanged
        where Impl : class, new()
    {
        private T GetLocalValue<T>(string name, T defaultValue)
        {
            try
            {
                var values = ApplicationData.Current.LocalSettings.Values;
                if (values.ContainsKey(name)) return (T)values[name];
                return defaultValue;
            }
            catch
            {
                return defaultValue;
            }
        }

        private void SetLocalValue<T>(string name, T value)
        {
            try
            {
                var settings = ApplicationData.Current.LocalSettings;
                if (settings.Values.ContainsKey(name))
                {
                    settings.Values[name] = value;
                }
                else
                {
                    settings.Values.Add(name, value);
                }
            }
            catch
            {
            }
        }

        private T GetRoamingValue<T>(string name, T defaultValue)
        {
            try
            {
                var values = ApplicationData.Current.RoamingSettings.Values;
                if (values.ContainsKey(name)) return (T)values[name];
                return defaultValue;
            }
            catch
            {
                return defaultValue;
            }
        }

        private void SetRoamingValue<T>(string name, T value)
        {
            try
            {
                var settings = ApplicationData.Current.RoamingSettings;
                if (settings.Values.ContainsKey(name))
                {
                    settings.Values[name] = value;
                }
                else
                {
                    settings.Values.Add(name, value);
                }
            }
            catch
            {
            }
        }

        private T GetValueProxy<T>(string name, T defaultValue)
        {
            var prop = GetType().GetRuntimeProperty(name);
            var attr = prop.GetCustomAttribute(typeof(LocalValueAttribute));
            return attr != null ? GetLocalValue(name, defaultValue) : GetRoamingValue(name, defaultValue);
        }

        private void SetValueProxy<T>(string name, T value)
        {
            var prop = GetType().GetRuntimeProperty(name);
            var attr = prop.GetCustomAttribute(typeof(LocalValueAttribute));
            if (attr != null) SetLocalValue(name, value);
            else SetRoamingValue(name, value);
        }

        protected T GetValue<T>([CallerMemberName] string name = null)
        {
            return GetValueProxy(name, default(T));
        }

        protected T GetValue<T>(T defaultValue, [CallerMemberName] string name = null)
        {
            return GetValueProxy(name, defaultValue);
        }

        protected void SetValue<T>(T value, [CallerMemberName] string name = null)
        {
            SetValueProxy(name, value);
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged([CallerMemberName] string name = null)
        {
            var h = PropertyChanged;
            if (h != null) h(this, new PropertyChangedEventArgs(name));
        }

        private static Impl _instance;
        public static Impl Instance { get { return _instance ?? (_instance = new Impl()); } }
        private static ResourceLoader _loader;
        public static ResourceLoader Loader { get { return _loader ?? (_loader = new ResourceLoader()); } }

        public static string GetString(string key)
        {
            return Loader.GetString(key);
        }

        protected AppConfigBase()
        {
        }

        protected virtual Impl CreateInstance()
        {
            return null;
        }
    }

    public class LocalValueAttribute : Attribute { }
}