<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="WpfApplication1.FELoaded" Loaded="OnLoad" Name="root"> </StackPanel> //File:Window.xaml.cs using System; using System.Windows; using System.Windows.Controls; namespace WpfApplication1 { public partial class FELoaded { void OnLoad(object sender, RoutedEventArgs e) { Button b1 = new Button(); b1.Content = "New Button"; root.Children.Add(b1); b1.Height = 25; b1.Width = 200; b1.HorizontalAlignment = HorizontalAlignment.Left; } } }