<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; } } } }