XAML Binding to the Title of a Window does not always work {Relative Source, AncestorType=Window}.

Question

Hi. I need to databind two TextBlocks to the Window Title property. The first one works via "RelativeSource FindAncestor, AncestorType=Window}", but the second one does not (it's deeply nested within a button tooltip).

How can I change the second one to make it also display the Title of the Window?

Thanks.

HorizontalAlignment="Stretch" VerticalAlignment="Center" Foreground="White" FontSize="18px" FontStretch="UltraExpanded" />

Accepted Answer

Hi,
you can use for instance of window an additional parameter (in ctor) to set string resource like in following demo:

XAML MainWindow:

ViewModel:

using System;  
using System.Windows;  
using System.Windows.Input;  
  
namespace WpfApp013  
{  
  public class ViewModel : ICommand  
  {  
  
    public void Execute(object parameter)  
    {  
      WpfApp1.Window013A wnd;  
      switch (parameter.ToString())  
      {  
        case "1":  
          wnd = new WpfApp1.Window013A("Title 1");  
          wnd.Show();  
          break;  
        case "2":  
          wnd = new WpfApp1.Window013A("Title 2");  
          wnd.Show();  
          break;  
        default:  
          break;  
      }  
    }  
  
    public event EventHandler CanExecuteChanged;  
    public bool CanExecute(object parameter) => true;  
  }  
}

Second Window with Title set in MainWindow:

And CodeBehind:

using System.Windows;  
  
namespace WpfApp1  
{  
  public partial class Window013A : Window  
  {  
    public Window013A(string title)  
    {  
      this.Resources.Add("Title", title);  
      InitializeComponent();  
    }  
  }  
}

Result:

Answer

HI,
your ToolTip is outside Window, see VisualTree:

You can use MVVM with Binding like this:

And CodeBehind and ViewModel:

Public Class Window068  
  Public Sub New()  
    Dim vm As New WpfApp068.ViewModel  
    Me.Resources.Add("vm", vm)  
    Me.DataContext = vm  
    ' This call is required by the designer.  
    InitializeComponent()  
  
    ' Add any initialization after the InitializeComponent() call.  
  
  End Sub  
End Class  
  
  
Namespace WpfApp068  
  Public Class ViewModel  
    Public Property Title As String = "new Title"  
  End Class  
End Namespace

Result:

Answer

Hi Peter. Thank you for explaining the Live Visual Tree. It helps me understand the whole picture.

My problem is that I cannot use the data straight from the ViewModel. The reason is that I have a single ViewModel, and many Views (Windows) setting their DataContext to that ViewModel.

So in my ViewModel I'm doing this kind of code:

            MyWindows.AddWindow(Content: new MyUserControl_1(this), // Different Views for the same ViewModel
                                    Owner: Owner,
                                    Title: "Title 1", // Different Title for each Window (to be displayed as a Tooltip)
                                    Width: 400,
                                    Height: 200,
                                    DataContext: this); // Same DataContext for the two Views

            MyWindows.AddWindow(Content: new MyUserControl_2(this), // Different Views for the same ViewModel
                                    Owner: Owner,
                                    Title: "Title 2", // Different Title for each Window (to be displayed as a Tooltip)
                                    Width: 400,
                                    Height: 200,
                                    DataContext: this); // Same DataContext for the two Views

Is there any hope with the current design?

Thank you.

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XAML Binding to the Title of a Window does not always work {Relative Source, AncestorType=Window}.

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