TextBlock Binding Fails When Placed in ContentControl with Content Set to Custom Helper [WinUI] #10584
Description
Describe the bug
In WinUI, the TextBlock binding does not work correctly when it is placed inside a ContentControl and the Content is set to a custom helper object. The same implementation works as expected in WPF.
**MainWindow.xaml**
<Grid x:Name="RootGrid" >
<StackPanel VerticalAlignment="Center" HorizontalAlignment="Center" Width="200">
<TextBlock Text="Enter the text below:" FontSize="15" FontWeight="SemiBold" Padding="10 0 0 0"/>
<TextBox Text="{Binding Path=MyText, Mode=TwoWay}"/>
<ContentControl x:Name="contentControl" Padding="10 0 0 0">
<ContentControl.ContentTemplate>
<DataTemplate>
<TextBlock x:Name="txtBlock" Text="{Binding Path=Value}" FontSize="20" Foreground="Blue"/>
</DataTemplate>
</ContentControl.ContentTemplate>
</ContentControl>
</StackPanel>
</Grid>
**MainWindow.xaml.cs**
public sealed partial class MainWindow : Window
{
public MyViewModel ViewModel { get; } = new MyViewModel();
public CustomHelper customHelper = new CustomHelper();
public MainWindow()
{
this.InitializeComponent();
RootGrid.DataContext = ViewModel;
Binding binding = new Binding
{
Path = new PropertyPath("MyText"),
Source = ViewModel,
Mode = BindingMode.OneWay
};
customHelper.SetValueBinding(binding);
contentControl.Content = customHelper;
}
}
**ViewModel**
public class MyViewModel : INotifyPropertyChanged
{
private string _myText;
public string MyText
{
get => _myText;
set
{
_myText = value;
OnPropertyChanged(nameof(MyText));
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name) =>
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
**CustomHelper**
public class CustomHelper : DependencyObject, INotifyPropertyChanged
{
public object Value
{
get { return GetValue(ValueProperty); }
set
{
SetValue(ValueProperty, value);
OnPropertyChanged("Value");
}
}
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value", typeof(object),
typeof(CustomHelper), new PropertyMetadata(null, OnValueChanged));
public event PropertyChangedEventHandler? PropertyChanged;
protected void OnPropertyChanged(string name) =>
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
}
public void SetValueBinding(BindingBase binding)
{
BindingOperations.SetBinding(this, ValueProperty, binding);
}
}
Steps to reproduce the bug
- Enter a value in the TextBox.
- Press the Tab key to commit the value.
Observed Behavior:
Value is not updated based on binding.
Expected behavior
The entered value should be reflected in the TextBlock because of binding.
Screenshots
WinUI Demo Video
WinUI_Demo.mp4
WPF Demo Video
WPF_Demo.mp4
NuGet package version
WinUI 3 - Windows App SDK 1.7.2: 1.7.250513003
Windows version
Windows 11 (24H2): Build 26100
Additional context
WinUI Sample - WinUI_SimpleSample.zip
WPF Sample - WPF_NetCoreSimpleSample.zip