Doing reactive/data-flow programming in C# is ludicrously verbose.

Single Reactive Property

    public class DrawingFeature : Feature
    {
        private Drawing drawing_;
        public event EventHandler DrawingChanged;
        private bool inDrawingChanged_;
        protected void OnDrawingChanged()
        {
            if (!inDrawingChanged_)
            {
                inDrawingChanged_ = true;
                try
                {
                    if (DrawingChanged != null)
                    {
                        DrawingChanged(this, EventArgs.Empty);
                    }
                    OnFeatureChanged();
                }
                finally
                {
                    inDrawingChanged_ = false;
                }
            }
        }
        public Drawing Drawing {
            get
            {
                return drawing_;
            }
            set
            {
                drawing_ = value;
                OnDrawingChanged();
            }
        }
    }