Changing graphical elements

   
   

<Window x:Class="ChangeItem.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Change Item">

  <Canvas x:Name="mainCanvas">
    <Ellipse Canvas.Left="10" Canvas.Top="30" Fill="Indigo" Width="40" Height="20" />
    <Ellipse Canvas.Left="20" Canvas.Top="40" Fill="Blue" Width="40" Height="20" />
    <Ellipse Canvas.Left="30" Canvas.Top="50" Fill="Cyan" Width="40" Height="20" />
    <Ellipse Canvas.Left="40" Canvas.Top="60" Fill="LightGreen" Width="40" Height="20" />
    <Ellipse Canvas.Left="50" Canvas.Top="70" Fill="Yellow" Width="40" Height="20" />
  </Canvas>
</Window>
//File:Window.xaml.cs
using System.Windows;
using System.Windows.Shapes;

namespace ChangeItem
{
    public partial class MainWindow : Window
    {
        public MainWindow(): base()
        {
            InitializeComponent();
            mainCanvas.MouseLeftButtonDown += OnClick;
        }

        private void OnClick(object sender, RoutedEventArgs e)
        {
            Ellipse r = e.Source as Ellipse;
            if (r != null)
            {
                r.Width += 10;
            }
        }
    }
}