StatefulView.cs

public abstract class StatefulView<TMessage,TModel> : View
	{
		public StatefulView() { }
		public StatefulView(TModel initialModel)
		{
			state = initialModel;
		}
		readonly State<TModel> state = new State<TModel>();
		public void Dispatch(TMessage message)
		{
			var model = Update(message, state.Value);
			state.Value = model;
		}

		[Body]
		View body() => View(state.Value);

		public abstract TModel Update(TMessage message, TModel model);

		public abstract View View(TModel model);
	}