AutoSuggestBox text property twoway binding error

[agonzalezrubio]

Describe the bug

Typing into the AutoSuggestBox text with a binding gives me this error

  <ui:AutoSuggestBox 
      x:Name="AdvancedTxtServer"
      Text="{Binding ServerSetup.ServerName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}"
      OriginalItemsSource="{Binding ServerList}" Icon="{ui:SymbolIcon Empty}"/>

This exception was originally thrown at this call stack:
    Wpf.Ui.Controls.AutoSuggestBox.TextPropertyChangedCallback(System.Windows.DependencyObject, System.Windows.DependencyPropertyChangedEventArgs) in AutoSuggestBox.cs
    System.Windows.DependencyObject.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs)
    System.Windows.FrameworkElement.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs)
    System.Windows.DependencyObject.NotifyPropertyChange(System.Windows.DependencyPropertyChangedEventArgs)
    System.Windows.DependencyObject.UpdateEffectiveValue(System.Windows.EntryIndex, System.Windows.DependencyProperty, System.Windows.PropertyMetadata, System.Windows.EffectiveValueEntry, ref System.Windows.EffectiveValueEntry, bool, bool, System.Windows.OperationType)
    System.Windows.DependencyObject.SetValueCommon(System.Windows.DependencyProperty, object, System.Windows.PropertyMetadata, bool, bool, System.Windows.OperationType, bool)
    System.Windows.DependencyObject.SetValue(System.Windows.DependencyProperty, object)
    MS.Internal.Xaml.Runtime.ClrObjectRuntime.SetValue(object, System.Xaml.XamlMember, object)

To Reproduce

Typing into the AutoSuggestBox text with a twoway binding

Expected behavior

No error

Screenshots

OS version

Windows 11

.NET version

.NET 7.0

WPF-UI NuGet version

3.0.0-preview.5

Additional context

No response

[agonzalezrubio]

[Redvo]

This happens because TextPropertyChangedCallback is static and called before TextBox is initialized in OnApplyTemplate.

From documentation on Text property:

/// <remarks>
/// This property is not typically set in XAML.
/// </remarks>

So probably a NULL check would be sufficient to not get exception there.

Now for your problem, what are you trying to achieve?

If you want to give AutoSuggestBox a default value, that is probably not a good idea and won't work. Changes in AutoSuggestBox source code are required for that.

If you want to update your ServerSetup.ServerName property when some text is typed into AutoSuggesBox, use OneWayToSource binding. This ensures the ServerName property is always updated when AutoSuggestBox text changes, but not other way around and it won't raise NullReferenceException at the begining.

If you want to set Property in your ViewModel after some option is chosen, that is only possible in code-behind in SuggestionChosen event for now, as far as I discovered:

<ui:AutoSuggestBox
  x:Name="AutoSuggestBox"
  SuggestionChosen="AutoSuggestBox_OnSuggestionChosen" ... />

private void AutoSuggestBox_OnSuggestionChosen(AutoSuggestBox sender, AutoSuggestBoxSuggestionChosenEventArgs args)
{
  ViewModel.ChosenOptionProperty = args.SelectedItem as MyOptionsItemType;
}

[agonzalezrubio]

Ohhhh, ok, thank you for your very useful response friend. Sorry I missed that! Lol.