class Test : INotifyPropertyChanged
    {
        int p;
        public int P
        {
            get { return p; }
            set { if (p == value) return; p = value; NotifyPropertyChanged(); }
        }

        void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
        {
            if (PropertyChangedInternal != null)
                PropertyChangedInternal(this, new PropertyChangedEventArgs(propertyName));
        }

        private event PropertyChangedEventHandler PropertyChangedInternal;

        public event PropertyChangedEventHandler PropertyChanged
        {
            add
            {
                WeakEventManager<Test, PropertyChangedEventArgs>.AddHandler(this, "PropertyChangedInternal", (sender, args) => value(sender, args));
            }
            remove
            {
                WeakEventManager<Test, PropertyChangedEventArgs>.RemoveHandler(this, "PropertyChangedInternal", (sender, args) => value(sender, args));
            }
        }
    }