WPF C#

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="Thumb_wcp.Pane1">
  
              Width="20" Height="20" 
          DragStarted="onDragStarted" DragCompleted="onDragCompleted"/>
  


//File:Window.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Documents;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Data;
using System.Windows.Media;
namespace Thumb_wcp
{
    public partial class Pane1 : Canvas
    {
        void onDragStarted(object sender, DragStartedEventArgs e)
        {
            myThumb.Background = Brushes.Orange;
        }
        void onDragCompleted(object sender, DragCompletedEventArgs e)
        {
            myThumb.Background = Brushes.Blue;
        }
    }
}