WPF Extensibility Hacks or WEX - Includes EventTrigger, ReactiveTrigger, InvokeMethodAction, InvokeCommandAction etc.

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Collections.Generic;
using System.Reflection;
using System.Globalization;
using System.Collections.ObjectModel;
using System.Reflection.Emit;
using System.Threading;

namespace Wex.Lib.Reactive
{
    #region Internal Classes from System.Reactive

    internal class AnonymousDisposable : IDisposable
    {
        // Fields
        private Action dispose;

        // Methods
        public AnonymousDisposable(Action dispose)
        {
            this.dispose = dispose;
        }

        public void Dispose()
        {
            this.dispose();
        }
    }

    internal class AnonymousObservable<T> : IObservable<T>
    {
        // Fields
        private Func<IObserver<T>, IDisposable> subscribe;

        // Methods
        public AnonymousObservable(Func<IObserver<T>, IDisposable> subscribe)
        {
            this.subscribe = subscribe;
        }

        public IDisposable Subscribe(IObserver<T> observer)
        {
            AsyncSubject<IDisposable> signal = new AsyncSubject<IDisposable>();
            var arg = new AutoDetachObserver(observer, signal);
            IDisposable disposable = this.subscribe(arg);
            signal.OnNext(disposable);
            return disposable;
        }

        // Nested Types
        private class AutoDetachObserver : AbstractObserver<T>
        {
            // Fields
            private IObserver<T> observer;
            private IObservable<IDisposable> signal;

            // Methods
            public AutoDetachObserver(IObserver<T> observer, IObservable<IDisposable> signal)
            {
                this.observer = observer;
                this.signal = signal;
            }

            protected override void Completed()
            {
                this.observer.OnCompleted();
                this.signal.Subscribe<IDisposable>(delegate(IDisposable d)
                {
                    d.Dispose();
                });
            }

            protected override void Error(Exception exception)
            {
                this.observer.OnError(exception);
                this.signal.Subscribe<IDisposable>(delegate(IDisposable d)
                {
                    d.Dispose();
                });
            }

            protected override void Next(T value)
            {
                this.observer.OnNext(value);
            }
        }
    }

    internal abstract class AbstractObserver<T> : IObserver<T>
    {
        // Fields
        private bool isStopped;

        // Methods
        public AbstractObserver()
        {
            this.isStopped = false;
        }

        protected abstract void Completed();
        protected abstract void Error(Exception exception);
        protected abstract void Next(T value);
        public void OnCompleted()
        {
            if (!this.isStopped)
            {
                this.isStopped = true;
                this.Completed();
            }
        }

        public void OnError(Exception exception)
        {
            if (!this.isStopped)
            {
                this.isStopped = true;
                this.Error(exception);
            }
        }

        public void OnNext(T value)
        {
            if (!this.isStopped)
            {
                this.Next(value);
            }
        }
    }

    #endregion
}