Exemplos de WPF 3.5 (Windows Presentation Foundation) - 002 - Sem usar o XAML

//Window1.cs
using System.Windows;
using System.Windows.Controls;
using System.Windows.Markup;


namespace _002_WPFCodeOnly
{
    class Window1 : Window
    {
        private Button button1;
        public Window1()
        {
            InitializeComponent();
        }


        private void InitializeComponent()
        {
            this.Width = this.Height = 285;
            this.Left = this.Top = 100;
            this.Title = "Somente código";


            DockPanel panel = new DockPanel();


            button1 = new Button();
            button1.Content = "Clique aqui";
            button1.Margin = new Thickness(30);

            button1.Click += button1_Click;

            IAddChild container = panel;
            container.AddChild(button1);

            container = this;

            container.AddChild(panel);
        }


        private void button1_Click(object sender, RoutedEventArgs e)
        {
            button1.Content = "Obedeceu, né???";
        }
    }
}

//program.cs
using System.Windows;
using System;


namespace _002_WPFCodeOnly
{
    public class Program : Application
    {
        [STAThread()]
        public static void Main()
        {
            Program app = new Program();
            app.MainWindow = new Window1();
            app.MainWindow.ShowDialog();
        }
    }
}