A generic variable wrapper that allows detecting value changes.

VariableChangedEventPattern.cs

using System;

namespace VariableChangedEventPattern
{
	class Program
	{
		private static void Main()
		{
			Game.Score.Changed += OnScoreChanged;
			Game.Score.Value += 200;
			Game.Score.Value += 50;

			Console.ReadKey();
		}

		private static void OnScoreChanged(object sender, ChangedEventArgs<int> e)
		{
			Console.WriteLine($"Score changed to {e.NewValue}!");
		}
	}

	static class Game
	{
		public static Changing<int> Score { get; private set; } = new Changing<int>();
	}

	class ChangedEventArgs<T> : EventArgs
	{
		public T OldValue { get; private set; }
		public T NewValue { get; private set; }

		public ChangedEventArgs(T oldValue, T newValue)
		{
			OldValue = oldValue;
			NewValue = newValue;
		}
	}

	class Changing<T>
	{
		public event EventHandler<ChangedEventArgs<T>> Changed;

		public T Value
		{
			get
			{
				return _value;
			}
			set
			{
				T oldValue = _value;
				_value = value;
				Changed?.Invoke(null, new ChangedEventArgs<T>(oldValue, _value));
			}
		}
		private T _value;

		public Changing(T value = default)
		{
			Value = value;
		}
	}
}