<Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Hello, WPF"> <Button x:Name="button" Width="200" Height="25" Click="button_Click">Click me</Button> </Window> //File:Window.xaml.cs using System; using System.Windows; using System.Windows.Controls; using System.Windows.Data; using System.Windows.Documents; using System.Windows.Media; using System.Windows.Shapes; namespace WpfApplication1{ public partial class Window1 : Window { public Window1() { InitializeComponent(); } void button_Click(object sender, RoutedEventArgs e) { MessageBox.Show("You", "Nice!"); } } }