using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Runtime.CompilerServices;

public class Program

{

    public static void Main()

    {

        var fb = new FizzyBuzzy();

        fb.PropertyChanged += (s, e) => {

            var _fb = s as FizzyBuzzy;

            if(e.PropertyName == "Value")

            {

                Console.WriteLine("{0:0000} {1}{2}", _fb.Value, _fb.Fizz(),_fb.Buzz());

            }

        };

        for(int i = 1; i <= 100; i++)

            fb.Value = i;

    }

    public class FizzyBuzzy : PropertyNotification

    {

        public int Value { get {return Get();} set {Set(value);} }

        public string Fizz()

        {

            return (Value % 3 == 0) ? "Fizz" : "";          

        }

        public string Buzz()

        {

            return (Value % 5 == 0) ? "Buzz" : "";          

        }

​

    }

    public abstract class PropertyNotification : INotifyPropertyChanged

    {

        private Dictionary<string, object> _p = new Dictionary<string, object>();

        private Dictionary<string, Type> _t = new Dictionary<string, Type>();

        private static Dictionary<Type, object> _d = new Dictionary<Type, object>();

​

        private static T GetDefault<T>() { return default(T); }

​

        protected dynamic Get([CallerMemberName] string name = null)

        {

            Type t = null;

            if(!_t.TryGetValue(name, out t))

            {   //this should only ever run once per property

                t = GetType().GetProperty(name).PropertyType;

                _t[name] = t;

            }

​

            object d = null;

            if(!_d.TryGetValue(t, out d))

            {   //this should only ever run once per type

                Func<object> f = GetDefault<object>;

                d = f.Method.GetGenericMethodDefinition().MakeGenericMethod(t).Invoke(null, null);

                _d[t] = d;

            }

​

            object v = null;

            if (_p.TryGetValue(name, out v))

                return v == null ? d : v;

​

            return d;

        }

​

        protected void Set<T>(T value, [CallerMemberName] string name = null)

        {

            if (Equals(value, Get(name)))

                return;

​

            _p[name] = value;

            _t[name] = value.GetType();

​

            OnPropertyChanged(name);

        }

​

        public event PropertyChangedEventHandler PropertyChanged;

​

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)

        {

            //PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

            PropertyChangedEventHandler handler = PropertyChanged;

            if (handler != null) {

                handler(this, new PropertyChangedEventArgs(propertyName));

            }

        }

​

    }

}