TechieSwitch-03.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace FormsIcons.Views
{

    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class TechieSwitch : ITechiesSwitchController
    {
        public static BindableProperty IsOnProperty = BindableProperty.Create(nameof(IsOn), typeof(bool),
            typeof(TechieSwitch), false, BindingMode.TwoWay, propertyChanged: OnPropertyChanged);        


        public TechieSwitch()
        {
            InitializeComponent();
        }
        public bool IsOn
        {
            get => (bool)GetValue(IsOnProperty);
            set
            {
                SetValue(IsOnProperty, value);                
            }
        }       

        private void ClickGestureRecognizer_OnClicked(object sender, EventArgs e)
        {            
            IsOn = !IsOn;
        }

        private static void OnPropertyChanged(BindableObject bindable, object oldvalue, object newvalue)
        {
            (bindable as ITechiesSwitchController).SetUITo((bool)newvalue);
        }        

        async void ITechiesSwitchController.SetUITo(bool valueToShow)
        {
            var position = new Rectangle
            {
                Left = 20,
                Top = 2,
                Width = 16,
                Height = 16
            };

            var uncheckedPosition = new Rectangle
            {
                Left = 2,
                Top = 2,
                Width = 16,
                Height = 16
            };

            await Thumb.LayoutTo(valueToShow ? position : uncheckedPosition, 300, Easing.SinIn);
        }
    }

    internal interface ITechiesSwitchController
    {
        void SetUITo(bool valueToShow);
    }
}