双重类型的DependencyProperty不会导致调用MeasureOverride()

Question

我正在做一个从FrameworkElement类派生的自定义滴答条指示符。我有一堆属性(附带的依赖项属性)定义指示器的外观和功能，例如Orientation和Range。Orientation是Orientation型，Range是double型。

从视图模型中更改Orientation将导致调用MeasureOverride()方法，允许我定义控件的新维度。但是，由于某些原因，更改Range属性不会(也不会更改其他double类型的属性)。我也搞不懂为什么。有谁知道这是为什么，以及如何让Range属性也调用MeasureOverride()

public class DepthIndicatorTickBar : FrameworkElement
{
    public static readonly DependencyProperty OrientationProperty =
        DependencyProperty.Register("Orientation", typeof(Orientation),
            typeof(DepthIndicatorTickBar),
            new FrameworkPropertyMetadata(Orientation.Horizontal,
                FrameworkPropertyMetadataOptions.AffectsRender));

    public static readonly DependencyProperty RangeProperty =
        DependencyProperty.Register("Range", typeof(double), 
            typeof(DepthIndicatorTickBar), 
            new FrameworkPropertyMetadata((double)100, 
                FrameworkPropertyMetadataOptions.AffectsRender));

    public Orientation Orientation
    {
        get { return (Orientation)GetValue(OrientationProperty); }
        set { SetValue(OrientationProperty, value); }
    }

    public double Range
    {
        get { return (double)GetValue(RangeProperty); }
        set { SetValue(RangeProperty, value); }
    }

    protected override Size MeasureOverride(Size availableSize)
    {
        Console.WriteLine("MeasureOverride");
        // Calculating new size
        return size;
    }

    protected override void OnRender(DrawingContext drawingContext)
    {
        Console.WriteLine("OnRender");
        // Drawing control
    }
}

Answer 1

如果要确保依赖项属性的值更改强制传递和重新呈现度量值，只需组合适当的FrameworkPropertyMetadataOptions标志：

public static readonly DependencyProperty RangeProperty = DependencyProperty.Register(
    nameof(Range),
    typeof(double), 
    typeof(DepthIndicatorTickBar), 
    new FrameworkPropertyMetadata(
        100d, 
        FrameworkPropertyMetadataOptions.AffectsMeasure |
        FrameworkPropertyMetadataOptions.AffectsRender));