Hello can any one help me to be able to set the data context for the window and page and uaer control for my winui3 app

Question

Hi I am creating a winui3 app and i have a 2 pages and I have a class that contains 2 Bindable properites and i want to set the data context for the 2 pages to be this class to be able to bind this bindable properites to the 2 pages elements. Thanks for every one

Answer 1

Hello @Omar Mohamed !

In WinUI 3, Window itself doesn’t have a DataContext property like WPF does, so you have to set it on the root element of your XAML tree (or use x:Bind which doesn’t require a DataContext at all).

Here’s way to share one view model instance across multiple pages and user controls that you can try

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Create your shared ViewModel

Make it implement INotifyPropertyChanged so bindings update automatically.

public class AppViewModel : INotifyPropertyChanged
{
    private string _firstProp;
    public string FirstProp
    {
        get => _firstProp;
        set { _firstProp = value; OnPropertyChanged(); }
    }
 
    private string _secondProp;
    public string SecondProp
    {
        get => _secondProp;
        set { _secondProp = value; OnPropertyChanged(); }
    }
 
    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged([CallerMemberName] string name = null) =>
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}

Instantiate it once and make it accessible

You can store it in App.xaml.cs so all pages can reuse the same instance.

public partial class App : Application
{
    public static AppViewModel SharedViewModel { get; } = new AppViewModel();
 
    protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
    {
        m_window = new MainWindow();
        m_window.Activate();
    }
 
    private Window m_window;
}

Set the DataContext in your Window/Page/UserControl

In your MainWindow.xaml

<Window
    x:Class="MyApp.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MyApp">
    <Grid x:Name="RootGrid">
        <Frame x:Name="MainFrame"/>
    </Grid>
</Window>

In your MainWindow.xaml.cs

public sealed partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        RootGrid.DataContext = App.SharedViewModel; // Set on root element
        MainFrame.Navigate(typeof(Page1));
    }
}

In each Page you can either:

• Inherit the DataContext from the Frame (if you don’t override it), or
• Explicitly set it in the page’s constructor.

public sealed partial class Page1 : Page
{
    public Page1()
    {
        InitializeComponent();
        DataContext = App.SharedViewModel; // Optional if inherited
    }
}
 

For UserControl, similar approach to set DataContext for shared instance, or bind it from the parent.

Example XAML binding

<TextBlock Text="{Binding FirstProp, Mode=TwoWay}"/>
<TextBox Text="{Binding SecondProp, Mode=TwoWay}"/>

By using one shared ViewModel as the DataContext for all pages and controls, you get consistent, synchronized data updates across your entire WinUI 3 app without duplicating state or wiring up extra events.

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I hope this helps! Let me know if you have any questions, if you find my answer is useful, feel free to mark this as final answer!