WPF draw thumbs on livecharts and drag drop thumb

//xaml
<Window x:Class="WpfApp299.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:lvc="clr-namespace:LiveCharts.Wpf;assembly=LiveCharts.Wpf"
        xmlns:local="clr-namespace:WpfApp299"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow">
    <Grid x:Name="gd">
        <Button HorizontalAlignment="Right" VerticalAlignment="Top" Width="200" Height="50" Click="Button_Click" 
                Panel.ZIndex="2">Refresh</Button>
        <Thumb x:Name="tb" Panel.ZIndex="10" Width="10" 
               DragStarted="Thumb_DragStarted"
               DragDelta="Thumb_DragDelta"
               DragCompleted="Thumb_DragCompleted"
               Height="{Binding Path=ActualHeight,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=Window}}">
            <Thumb.Template>
                <ControlTemplate>
                    <Rectangle>
                        <Rectangle.Fill>Red</Rectangle.Fill>
                    </Rectangle>
                </ControlTemplate>
            </Thumb.Template>
        </Thumb>
        
        <lvc:CartesianChart x:Name="chart" Series="{Binding BooksCollection,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" 
                            LegendLocation="Right"
                            MouseDown="CartesianChart_MouseDown" Panel.ZIndex="1">
            <lvc:CartesianChart.AxisX>
                <lvc:Axis Title="Salesman" Labels="{Binding Labels,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>
            </lvc:CartesianChart.AxisX>
            <lvc:CartesianChart.AxisY>
                <lvc:Axis Title="Sold Apps" LabelFormatter="{Binding Formatter}"/>
            </lvc:CartesianChart.AxisY>
        </lvc:CartesianChart>
    </Grid>
</Window>




//cs
using System;
using System.CodeDom;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using LiveCharts;
using LiveCharts.Wpf;
using Newtonsoft.Json;

namespace WpfApp299
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, INotifyPropertyChanged
    {

        private int idx = 0;
        public MainWindow()
        {
            InitializeComponent();
            rnd = new Random();
            this.DataContext = this;
            InitData();
        }

        
        private void InitData()
        {           
            BooksCollection = new SeriesCollection();
            BooksCollection.Add(new ColumnSeries
            {
                Title = "2015",
                Values=new ChartValues<double> { rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1,1000) }
            });

            BooksCollection.Add(new ColumnSeries
            {
                Title = "2016",
                Values = new ChartValues<double> { rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000) }
            });

            BooksCollection.Add(new ColumnSeries
            {
                Title = "2017",
                Values = new ChartValues<double> { rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000) }
            });

            BooksCollection.Add(new ColumnSeries
            {
                Title = "2018",
                Values = new ChartValues<double> { rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000) }
            });

            BooksCollection.Add(new ColumnSeries
            {
                Title = "2019",
                Values = new ChartValues<double> { rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000), rnd.Next(1, 1000) }
            });
            
            Labels = new List<string>();
            for(int i=0;i<5;i++)
            {
                Labels.Add($"SalesMan_{rnd.Next(1,100)}");
            }
        }

        private Random rnd { get; set; }

        private SeriesCollection booksCollection;
        public SeriesCollection BooksCollection
        {
            get
            {
                return booksCollection;
            }
            set
            {
                booksCollection = value;
                OnPropertyChanged(nameof(BooksCollection));
            }
        }

        private List<string> labels;
        public List<string> Labels
        {
            get
            {
                return labels;
            }
            set
            {
                if(value!=labels)
                {
                    labels = value;
                    OnPropertyChanged(nameof(Labels));
                }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        
        private void OnPropertyChanged(string propName)
        {
            var handler = PropertyChanged;
            if(handler!=null)
            {
                handler?.Invoke(this, new PropertyChangedEventArgs(propName));
            }
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Application.Current.Dispatcher.BeginInvoke(new Action(() =>
            {
                InitData();
            }));
            //Task.Run(() =>
            //{
            //    InitData();
            //});
        }

        private void Thumb_DragStarted(object sender, System.Windows.Controls.Primitives.DragStartedEventArgs e)
        {

        }

        private void Thumb_DragDelta(object sender, System.Windows.Controls.Primitives.DragDeltaEventArgs e)
        {
            
        }

        private void Thumb_DragCompleted(object sender, System.Windows.Controls.Primitives.DragCompletedEventArgs e)
        {
            var margin = tb.Margin.Left;
            var xDelta = e.HorizontalChange;
            tb.Margin = new Thickness(tb.Margin.Left + xDelta, 0, 0, 0);
        }

        int zIndex = 20;
        private void CartesianChart_MouseDown(object sender, MouseButtonEventArgs e)
        {
            var pt = e.GetPosition(this);
            Thumb newTb = new Thumb();
            newTb.Width = 10;
            newTb.Background = new SolidColorBrush(Colors.Red);
            newTb.BorderBrush = new SolidColorBrush(Colors.Red);
            newTb.Margin = new Thickness(pt.X, 0, 0, 0);
            chart.Width = this.ActualWidth;
            Grid.SetZIndex(newTb, 10);             
            gd.Children.Add(newTb);
        } 
    }

    public class  BookTrim
    {
        public string Title { get; set; }
        public string Values { get; set; }
    }
}