UserControl DependencyProperty propertyChangedCallback not called - wpf

Question

So I have an ItemsControl set in my xaml as such:
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<local:ToggleButton Command="{Binding DataContext.ItemSelectedCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type WrapPanel}}}"
CommandParameter="{Binding DataContext, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid}}}"
Text="{Binding DataContext.ItemEnum, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid}}, Converter={StaticResource EnumToStringConverter}}"
IsActive="{Binding DataContext.Selected, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid}}, UpdateSourceTrigger=PropertyChanged}"
Width="96"
Height="88"
Margin="5" />
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I have the 4 dependency properties Command, CommandParameter, Text, and IsActive.
The first 3 dependency properties work correctly, the text is set, and the command callback works with the parameter.
The IsActive property however does NOT work.
The Items property in the main viewmodel is defined as:
List<ItemViewModel> Items { get; set; }
The ItemViewModel is defined as:
public class ItemViewModel : INotifyPropertyChanged
{
public ItemViewModel()
{
this.Selected = true;
}
private bool? _selected;
public event PropertyChangedEventHandler PropertyChanged;
public ItemEnum ItemEnum { get; set; }
public bool? Selected
{
get { return this._selected; }
set
{
this._selected = value;
this.OnPropertyChanged(nameof(this.Selected));
}
}
protected virtual void OnPropertyChanged(string propertyName = null)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
the dependency property for the IsActive property in the ToggleButton.xaml.cs file looks like:
public static readonly DependencyProperty IsActiveProperty = DependencyProperty.Register(nameof(IsActive), typeof(bool?), typeof(ToggleButton), new PropertyMetadata(null, IsActiveSetCallback));
private static void IsActiveSetCallback(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var button = (ToggleButton)obj;
button.IsActive = (bool)(e.NewValue ?? e.OldValue);0xa5, 0xa5));
}
My command callback in the main view model looks like this:
this.ItemSelectedCommand =
new DelegateCommand(
itemVm =>
{
bool? setTo = !((ItemViewModel) itemVm).Selected;
this.Items.ForEach(i => i.Selected = false);
((ItemViewModel) itemVm).Selected = setTo;
});
Again, the other dependency properties (defined basically identically to IsActiveProperty) work correctly, so when I click the item, the above command gets called (verified by breakpoint), the item's Selected flag gets toggled properly, but the IsActiveSetCallback never gets hit. I can't see what I'm doing wrong, but clearly it's something.
Does anyone see something that I don't?
Thanks in advance!

Answer 1

After spending too much time trying to solve this, of course I manage to solve it myself within half an hour of posting this question..
I pulled this from the Microsoft DependencyProperty docs, specifically the section about 'Dependency Property Setting Precedence List':
Local value. A local value might be set through the convenience of the "wrapper" property, which also equates to setting as an attribute or property element in XAML, or by a call to the SetValue API using a property of a specific instance. If you set a local value by using a binding or a resource, these each act in the precedence as if a direct value was set.
So, I was setting this.Active in two places in the ToggleButton.xaml.cs, once in the constructor as a default value, and once in the IsActiveSetCallback .. turns out by doing that, I was overriding the binding, and neither of those calls were necessary anyways. So simple!