Using RX for object level CQRS, method proxy and logging.

reactive.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reactive.Subjects;
using System.Reactive.Linq;

namespace FpCs
{
    class Program
    {
        static void Main(string[] args)
        {    
            var test = new Proto();
            test.SetI.Subscribe(i => Console.WriteLine("New I = " + i));
            var sSubscr = test.SetS.Subscribe(s => Console.WriteLine("New S = " + s));

            test.SetI.Select(i => test)
                .Merge(test.SetS.Select(i => test)).Select((proto, index) => new { P = proto, I = index + 1 })
                .Subscribe(s => Console.WriteLine("Proto after change " + s.P + " this is " + s.I + " change"));

            test.SetI.OnNext(1);
            test.SetS.OnNext("s");
            sSubscr.Dispose();
            test.SetS.OnNext("new s");

            Action<int, ISubject<int>> proxy = (i, old) => old.OnNext(i + 1);

            proxy.AddAsBeforeProxyTo(ref test.SetI);
            test.SetI.OnNext(5);

            Console.ReadKey();
        }

       
    }

    public class Proto
    {
        public Proto()
        {
            var i = 0;// like a fields
            var s = "";

            SetI = new Subject<int>();
            SetI.Subscribe(ni => i = ni);

            SetS = new Subject<String>();
            SetS.Subscribe(ns => s = ns);

            GetI = () => i;
            GetS = () => s;
        }

        public ISubject<int> SetI; //like a properties
        public Func<int> GetI;

        public ISubject<string> SetS;
        public Func<string> GetS;

        public override string ToString()
        {
            return String.Format("{{s={0} i={1}}}", GetS(), GetI());
        }
       
    }

    public static class SubjectHelper
    {
        //Need to rtfm to know how to do it correctly
        public static void AddAsBeforeProxyTo<T>(this Action<T, ISubject<T>> proxy, ref ISubject<T> acc)
        {
            var p = new Subject<T>();
            var old = acc;
            p.Subscribe(x => proxy(x, old));
            acc = p;
        }
    }
}

Output:
New I = 1
Proto after change {s= i=1} this is 1 change
New S = s
Proto after change {s=s i=1} this is 2 change
Proto after change {s=new s i=1} this is 3 change
New I = 6
Proto after change {s=new s i=6} this is 4 change