如何在WPF中添加用户名？

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="WPF Username Example" Height="350" Width="500">
    <Grid>
        <Label Content="Username:" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10"/>
        <TextBox x:Name="txtUsername" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="80,5,0,0" Width="200" TextChanged="txtUsername_TextChanged"/>
        <Label x:Name="lblUsername" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,30,0,0"/>
    </Grid>
</Window>

using System.Windows;

namespace WpfApp1
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void txtUsername_TextChanged(object sender, TextChangedEventArgs e)
        {
            lblUsername.Content = txtUsername.Text;
        }
    }
}