WPF knowledge Raiders 09- Additional Properties

Additional attributes is a special dependency property.

Canvas in Canvas.Left, Canvas.Top, DockPanel in DockPanel.Dock and so is the additional properties.

More .NET class properties wording experience. This can directly point out, are not examples of static. Top property with an example:

public static readonly DependencyProperty TopProperty =
    DependencyProperty.RegisterAttached("Top", 
    typeof(double), typeof(Canvas),
    new FrameworkPropertyMetadata(0d,
        FrameworkPropertyMetadataOptions.Inherits));
 
public static void SetTop(UIElement element, double value)
{
    element.SetValue(TopProperty, value);
}
 
public static double GetTop(UIElement element)
{
    return (double)element.GetValue(TopProperty);
}

 See effects following code:

<Canvas Background="#AAAAAA" Height="150" Width="200">
    <Rectangle Canvas.Left="50" Canvas.Top="50" Width="50" Height="50" Fill="Red" />
</Canvas>

The code can be seen on Rectangle Left property of Canvas, the actual effect on the actual role Convas.Top additional property attributes Rectangle Top Convas.Left additional property of Canvas.

Let's look at an example:

<Grid>
    <Grid.Clip>
        <EllipseGeometry Center="400 200" RadiusX="160" RadiusY="200" />
    </Grid.Clip>
    <Image Source="ping.jpg" Stretch="Fill" />
</Grid>

Clip Grid by additional attributes we intercepted the desired picture effect.

 So when to use additional attributes? Here is a classic Material Design theme WPF open source projects Material Design In XAML Toolkit in the shaded part of the process for the source.

public static class ShadowAssist
    {
        public static readonly DependencyProperty ShadowDepthProperty = DependencyProperty.RegisterAttached(
            "ShadowDepth", typeof (ShadowDepth), typeof (ShadowAssist), new FrameworkPropertyMetadata(default(ShadowDepth), FrameworkPropertyMetadataOptions.AffectsRender));

        public static void SetShadowDepth(DependencyObject element, ShadowDepth value)
        {
            element.SetValue(ShadowDepthProperty, value);
        }

        public static ShadowDepth GetShadowDepth(DependencyObject element)
        {
            return (ShadowDepth) element.GetValue(ShadowDepthProperty);
        }

        private static readonly DependencyPropertyKey LocalInfoPropertyKey = DependencyProperty.RegisterAttachedReadOnly(
            "LocalInfo", typeof (ShadowLocalInfo), typeof (ShadowAssist), new PropertyMetadata(default(ShadowLocalInfo)));

        private static void SetLocalInfo(DependencyObject element, ShadowLocalInfo value)
        {
            element.SetValue(LocalInfoPropertyKey, value);
        }

        private static ShadowLocalInfo GetLocalInfo(DependencyObject element)
        {
            return (ShadowLocalInfo) element.GetValue(LocalInfoPropertyKey.DependencyProperty);
        }

        public static readonly DependencyProperty DarkenProperty = DependencyProperty.RegisterAttached(
            "Darken", typeof (bool), typeof (ShadowAssist), new FrameworkPropertyMetadata(default(bool), FrameworkPropertyMetadataOptions.AffectsRender, DarkenPropertyChangedCallback));

        private static void DarkenPropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
        {
            var uiElement = dependencyObject as UIElement;
            var dropShadowEffect = uiElement?.Effect as DropShadowEffect;

            if (dropShadowEffect == null) return;

            if ((bool) dependencyPropertyChangedEventArgs.NewValue)
            {
                SetLocalInfo(dependencyObject, new ShadowLocalInfo(dropShadowEffect.Opacity));

                var doubleAnimation = new DoubleAnimation(1, new Duration(TimeSpan.FromMilliseconds(350)))
                {
                    FillBehavior = FillBehavior.HoldEnd
                };
                dropShadowEffect.BeginAnimation(DropShadowEffect.OpacityProperty, doubleAnimation);                
            }
            else
            {
                var shadowLocalInfo = GetLocalInfo(dependencyObject);
                if (shadowLocalInfo == null) return;

                var doubleAnimation = new DoubleAnimation(shadowLocalInfo.StandardOpacity, new Duration(TimeSpan.FromMilliseconds(350)))
                {
                    FillBehavior = FillBehavior.HoldEnd
                };
                dropShadowEffect.BeginAnimation(DropShadowEffect.OpacityProperty, doubleAnimation);
            }
        }

        public static void SetDarken(DependencyObject element, bool value)
        {
            element.SetValue(DarkenProperty, value);
        }

        public static bool GetDarken(DependencyObject element)
        {
            return (bool) element.GetValue(DarkenProperty);
        }

        public static readonly DependencyProperty CacheModeProperty = DependencyProperty.RegisterAttached(
            "CacheMode", typeof(CacheMode), typeof(ShadowAssist), new FrameworkPropertyMetadata(new BitmapCache { EnableClearType = true, SnapsToDevicePixels = true }, FrameworkPropertyMetadataOptions.Inherits));

        public static void SetCacheMode(DependencyObject element, CacheMode value)
        {
            element.SetValue(CacheModeProperty, value);
        }

        public static CacheMode GetCacheMode(DependencyObject element)
        {
            return (CacheMode)element.GetValue(CacheModeProperty);
        }

        public static readonly DependencyProperty ShadowEdgesProperty = DependencyProperty.RegisterAttached(
            "ShadowEdges", typeof(ShadowEdges), typeof(ShadowAssist), new PropertyMetadata(ShadowEdges.All));

        public static void SetShadowEdges(DependencyObject element, ShadowEdges value)
        {
            element.SetValue(ShadowEdgesProperty, value);
        }

        public static ShadowEdges GetShadowEdges(DependencyObject element)
        {
            return (ShadowEdges) element.GetValue(ShadowEdgesProperty);
        }
    }

<Setter Property="wpf:ShadowAssist.ShadowDepth" Value="Depth1" />

Google's "material design" concept, the shadow is the more important part, and the project is the use of additional attributes to achieve the effect. Which there are many properties is done through the additional property, give me how to use the additional property, providing good template.

Can refer to learn: https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit