WPF thumb Drag DragDelta,DragStarted,DragCompleted

//xaml
<Window x:Class="WpfApp302.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:local="clr-namespace:WpfApp302"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <Style TargetType="Thumb">
            
        </Style>
    </Window.Resources>
    <Grid>
        <Canvas x:Name="cvs" Panel.ZIndex="2" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">            
            <Thumb x:Name="tb" Canvas.Left="100" Canvas.Top="0"
                   Background="Blue" Width="15" 
                   Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=Canvas}}" 
                   DragDelta="tb_DragDelta"
                   DragStarted="tb_DragStarted" DragCompleted="tb_DragCompleted">
                <Thumb.Template>
                    <ControlTemplate>
                        <Border BorderBrush="Black" BorderThickness="2">
                            <Rectangle Fill="Blue"/>
                        </Border>
                    </ControlTemplate>
                </Thumb.Template>
            </Thumb>
        </Canvas> 
    </Grid>
</Window>




//cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
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;

namespace WpfApp302
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            LinearGradientBrush lineBrush = new LinearGradientBrush();
            lineBrush.StartPoint = new Point(0, 0);
            lineBrush.EndPoint = new Point(1, 1);
            GradientStop gs1 = new GradientStop();
            gs1.Offset = 0;
            gs1.Color = Colors.Red;
            lineBrush.GradientStops.Add(gs1);
            GradientStop gs2 = new GradientStop();
            gs2.Offset = 0.25;
            gs2.Color = Colors.Brown;
            lineBrush.GradientStops.Add(gs2);
            GradientStop gs3 = new GradientStop();
            gs3.Offset = 0.5;
            gs3.Color = Colors.OrangeRed;
            lineBrush.GradientStops.Add(gs3);
            GradientStop gs4=new GradientStop();
            gs4.Offset = 0.75;
            gs4.Color = Colors.Orange;
            lineBrush.GradientStops.Add(gs4);
            GradientStop gs5 = new GradientStop();
            gs5.Offset = 1;
            gs5.Color = Colors.Yellow;
            lineBrush.GradientStops.Add(gs5);
            cvs.Background= lineBrush;
        }

        private void tb_DragDelta(object sender, System.Windows.Controls.Primitives.DragDeltaEventArgs e)
        {
            double xValue = Canvas.GetLeft(tb) + e.HorizontalChange;
            Canvas.SetLeft(tb, xValue);
            //Canvas.SetTop(tb, Canvas.GetTop(tb) + e.VerticalChange);
            this.Title = $"X:{xValue}";
            double yadjust = cvs.Height + e.VerticalChange;
            double xadjust = cvs.Width + e.HorizontalChange;

            if((xadjust>=0) && (yadjust>=0))
            { 
               
            }
        }

        private void tb_DragStarted(object sender, System.Windows.Controls.Primitives.DragStartedEventArgs e)
        {
            tb.Background = Brushes.Orange;
        }

        private void tb_DragCompleted(object sender, System.Windows.Controls.Primitives.DragCompletedEventArgs e)
        {
            tb.Background = Brushes.Blue;
        }
    }
}