<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="MyNameSpace.IncludeApplicationDefinition.MyWindow" Title="Include Application Definition" SizeToContent="WidthAndHeight" ResizeMode="CanMinimize"> <Button HorizontalAlignment="Center" VerticalAlignment="Center" Margin="1.5in" Click="ButtonOnClick"> Click </Button> </Window> //File:Window.xaml.cs using System; using System.Windows; using System.Windows.Controls; using System.Windows.Input; namespace MyNameSpace.IncludeApplicationDefinition { public partial class MyWindow : Window { public MyWindow() { InitializeComponent(); } void ButtonOnClick(object sender, RoutedEventArgs args) { Button btn = sender as Button; MessageBox.Show(btn.Content + "' has been clicked."); } } }