c# wpf从另一个窗口更改对象的属性

<Window x:Class="WpfApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel>
        <TextBlock Text="{Binding Path=UserName}" FontSize="20"/>
        <Button Content="Open Settings" Click="OpenSettings_Click"/>
    </StackPanel>
</Window>

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new UserSettings();
    }

    private void OpenSettings_Click(object sender, RoutedEventArgs e)
    {
        var settingsWindow = new SettingsWindow();
        settingsWindow.DataContext = DataContext;
        settingsWindow.ShowDialog();
    }
}

public class UserSettings : INotifyPropertyChanged
{
    private string _userName;
    public string UserName
    {
        get => _userName;
        set
        {
            _userName = value;
            OnPropertyChanged(nameof(UserName));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

<Window x:Class="WpfApp.SettingsWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="SettingsWindow" Height="200" Width="300">
    <StackPanel>
        <TextBox Text="{Binding Path=UserName, Mode=TwoWay}" FontSize="16"/>
        <Button Content="Save" Click="Save_Click"/>
    </StackPanel>
</Window>

public partial class SettingsWindow : Window
{
    public SettingsWindow()
    {
        InitializeComponent();
    }

    private void Save_Click(object sender, RoutedEventArgs e)
    {
        DialogResult = true;
        Close();
    }
}