How to Trigger Callbacks on Dependency Property Changes from XAML?

Handling callbacks for dependency property changes in XAML

When setting a value for a dependency property at runtime, the corresponding OnPropertyChanged method is called immediately. However, these callbacks remain dormant while the designer assigns property values ​​via XAML. This behavior stems from the efficiency of using the property system's SetValue methods directly, bypassing the property wrapper setter methods. So the logic in the property wrapper has no effect in this case.

To resolve this issue, please register a PropertyChangedCallback using attribute metadata:

<code class="language-csharp">public static readonly DependencyProperty IsClosedProperty =
    DependencyProperty.Register(
        "IsClosed", typeof(bool), typeof(GroupBox),
        new FrameworkPropertyMetadata(false,
            FrameworkPropertyMetadataOptions.AffectsRender,
            (o, e) => ((GroupBox)o).OnIsClosedChanged()));

public bool IsClosed
{
    get { return (bool)GetValue(IsClosedProperty); }
    set { SetValue(IsClosedProperty, value); }
}

private void OnIsClosedChanged()
{
    _rowDefContent.Height = new GridLength((IsClosed ? 0 : 1), GridUnitType.Star);
}</code>

This approach ensures that the OnIsClosedChanged method is executed when the IsClosed property value is modified, regardless of the source being XAML, binding, etc.

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