FrameworkElementFactory textBox = new FrameworkElementFactory(typeof(TextBox));
textBox.AddHandler(TextBox.LoadedEvent, new RoutedEventHandler(OnTextBoxLoaded));
private void OnTextBoxLoaded(object sender, RoutedEventArgs e)
{
TextBox textBox = sender as TextBox;
if (textBox != null)
{
textBox.Focus();
}
}