Designer DependencyProperty and WPF

Question

class MyLine : Shape { public static readonly DependencyProperty X11Property; public static readonly DependencyProperty X22Property; public static readonly DependencyProperty Y11Property; public static readonly DependencyProperty Y22Property; static MyLine() { X11Property = DependencyProperty.Register("X11", typeof(double), typeof(MyLine), new UIPropertyMetadata(double.NaN)); X22Property = DependencyProperty.Register("X22", typeof(double), typeof(MyLine), new UIPropertyMetadata(double.NaN)); Y11Property = DependencyProperty.Register("Y11", typeof(double), typeof(MyLine), new UIPropertyMetadata(double.NaN)); Y22Property = DependencyProperty.Register("Y22", typeof(double), typeof(MyLine), new UIPropertyMetadata(double.NaN)); } [TypeConverter(typeof(LengthConverter))] public double X11 { get { return (double)GetValue(X11Property); } set { SetValue(X11Property, value); } } [TypeConverter(typeof(LengthConverter))] public double X22 { get { return (double)GetValue(X22Property); } set { SetValue(X22Property, value); } } [TypeConverter(typeof(LengthConverter))] public double Y11 { get { return (double)GetValue(Y11Property); } set { SetValue(Y11Property, value); } } [TypeConverter(typeof(LengthConverter))] public double Y22 { get { return (double)GetValue(Y22Property); } set { SetValue(Y22Property, value); } } protected override System.Windows.Media.Geometry DefiningGeometry { get { var geometryGroup = new GeometryGroup(); // Add line geometryGroup.Children.Add(new LineGeometry(new Point(X11, Y11), new Point(X22, Y22))); return geometryGroup; } } } 

Why, when I update myLine coordinates in the WPF designer (VS 2010), does it not update it automatically (live)?

When using the default WPF Line objects, they are automatically updated when the XAML code changes (is edited) in the XAML / Design view.

Answer 1

Since these properties affect rendering, you must specify it in the metadata:

 X11Property = DependencyProperty.Register("X11", typeof(double), typeof(DirectionLine), new FrameworkPropertyMetadata(double.NaN, FrameworkPropertyMetadataOptions.AffectsRender)); 

I'm not sure that the developer will have enough to consider this, but it’s worth a try ...