simply_shape_moving_by_xamarin_with_rx

MainActivity.cs

using System;

using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.Reactive.Linq;
using NDebug = System.Diagnostics.Debug;
using Android.Graphics;

namespace DrawingTest
{
    [Activity(Label = "DrawingTest", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);
            ActionBar.Hide();

            var rectangle = FindViewById<View>(Resource.Id.view1);
            rectangle.DownEvent()
                .SelectMany(rectangle.MoveEvent())
                .Subscribe(e =>
                {
                    rectangle.SetX(e.RawX);
                    rectangle.SetY(e.RawY - 50f);
                });
        }
    }
}

ViewExtensions.cs

using System;
using Android.Views;
using System.Reactive.Linq;

namespace DrawingTest
{
    public static class ViewExtensions
    {
        public static IObservable<MotionEvent> DownEvent(this View v)
        {
            return Observable.FromEventPattern<View.TouchEventArgs>(h => v.Touch += h, h => v.Touch -= h)
                .Where(e => e.EventArgs.Event.Action == MotionEventActions.Down)
                .Select(e => e.EventArgs.Event);
        }

        public static IObservable<MotionEvent> MoveEvent(this View v)
        {
            return Observable.FromEventPattern<View.TouchEventArgs>(h => v.Touch += h, h => v.Touch -= h)
                .Where(e => e.EventArgs.Event.Action == MotionEventActions.Move)
                .Select(e => e.EventArgs.Event);
        }

    }
}