winui 3 FindAncestor

Question

winui 3 FindAncestor

Simon Ong 21

Hello:

 In Wpf ,  The below code in a page/usercontrol will get the property value from MainWindow Datacontext.

                    <TextBlock  Text="{Binding DataContext.Arr[2],RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}"/>

What is the equivalent in Winui?

Assuming the MainViewModel is set at MainWindow.xaml.cs as

public MainViewModel mvm { get; } = new();

Regards

Simon

1 answer

Your answer

Answer 1

Jeanine Zhang-MSFT 11,356 Microsoft External Staff

Hello,

Welcome to Microsoft Q&A!

As far as I'm concerned, the RelativeSource property in WinUI3 is not support the FindAncestor mode.

If you want to bind to a property of a parent element in the visual tree, you could try to set the ElementName property of the binding to the name of the ancestor element to bind to instead of using a RelativeSource.

And you could try to create a Custom attached properties that sets the DataContext of the target element to a parent element of a specific type.

Thank you.

Jeanine

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Simon Ong 21

Hi Jeanine:

             Both suggestions are not working.  Let me give a clearer picture,

The MainWindow consists of ContentControl which has a content binding to aan object.( name of CurrentContent)

The MainWindow "Datacontext" is bound with ViewModel with the name of Mvm. The Mvm is initialized during Window loading.

The CurrentContent will have an object loaded (a UserControl with a simple Textblock).

In the Mvm, there is a string property RuntimeStr wh

  UserPage Page1; 
public MainViewModel()
 {
     Page1= new UserPage();
     CurrentContent = Page1;
     RuntimeStr = "Hello Wirkd";
 }

 [ObservableProperty]
 private object _currentContent;

[ObservableProperty]
 private string _runtimeStr;

        public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("RuntimeStr", typeof(string), typeof(MainWindow), new PropertyMetadata("AAA"));

   <TextBlock x:Name="T" Text="{Binding RuntimeStr,ElementName=Mwindow}" />

//x:Name="Mwindow" is the name of MainWindow that consists of ContentControl

Is there anyway or am I doing wrong?

Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-12-05T06:51:11.3633333+00:00

When the target and source elements reside in different XAML namescopes or when the source element has been created dynamically, this doesn’t work.

I recommended that you try to use the second method: use a custom attached property to bind.

You could refer to the sample: https://github.com/mgnsm/CodeSamples/tree/master/BindingToParentElementSample
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-12-12T05:38:23.6233333+00:00

Have you got any updates about this issue? Could you please check my suggestion?
Eason Yao 0 Reputation points

2023-12-26T12:45:10.0333333+00:00

Hi Jeanine:

When using ElementName in binding, does it target to the nearest ancestor or the first element from root? if the ancestor is a template and may duplicated several times?
Shimmy Weitzhandler 291 Reputation points

2024-12-16T16:51:53.13+00:00

The problem with ElementName is that it can't be used in a StaticResource as the binding only operates as a OneTime mode and doesn't update when a property changes.
Shimmy Weitzhandler 291 Reputation points

2025-03-28T11:47:11.45+00:00

obj.Parent and VisualTreeHelper.GetParent both return null

Share via

winui 3 FindAncestor

1 answer

Your answer