Getting that sweet, sweet `didSet` functionality in C#.

PropertyBox.cs

using System;
using System.Collections;
using System.Collections.Generic;

public class PropertyBox<T>
{
    private T value;
    public Action<T> didSet;
    public Action<T,T> willSet;

    public T get() {
        return value;
    }

    public static PropertyBox<Q> withValue<Q>(Q val) {
        return new PropertyBox<Q>() { value = val };
    }

    public void set(T val) {
        if (willSet != null) {
            willSet(value, val);
        }
        value = val;
        if (didSet != null) {
            didSet(val);
        }
    }
}