在列表框中使用径向面板，抛出异常VisualTree单元素

public static readonly DependencyProperty RadiusProperty = DependencyProperty.Register("Radius", typeof(double), typeof(CircularPanel), new PropertyMetadata(50.0, new PropertyChangedCallback(RadiusChanged)));

private static void RadiusChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e) { ((CircularPanel)sender).Refresh(); }

<ItemsPanelTemplate x:Key="ItemsPanelTemplate2">
        <WpfApplication7:CircularPanel d:LayoutOverrides="Width, Height" AngleItem="{Binding Angle}" AnimationDuration="75" Radius="0" InitialAngle="90"/>
</ItemsPanelTemplate>

<ListBox ItemsPanel="{StaticResource ItemsPanelTemplate2}" ItemContainerStyle="{StaticResource ListBoxItemStyle1}" ItemsSource="{Binding Hosts, Mode=OneWay}" >