关于.net：WPF中鼠标下A型控件的计数

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<UserControl x:Class="WpfApplication7.UserControl1">
    <Grid>
        <Label Content="Label" Height="44" HorizontalAlignment="Left" Name="label1" VerticalAlignment="Top" FontSize="20" FontWeight="Bold" Width="78" Background="#FF4B9FC4" BorderBrush="#FF020A0D" BorderThickness="1" />
    </Grid>
</UserControl>

<Window x:Class="WpfApplication7.MainWindow"
PreviewMouseLeftButtonDown="Window_PreviewMouseLeftButtonDown" xmlns:my="clr-namespace:WpfApplication7">
    <Grid>
        <my:UserControl1 HorizontalAlignment="Left" Margin="82,88,0,0" x:Name="userControl11" VerticalAlignment="Top" />
        <my:UserControl1 HorizontalAlignment="Left" Margin="168,166,0,0" x:Name="userControl12" VerticalAlignment="Top" />
        <my:UserControl1 HorizontalAlignment="Left" Margin="231,130,0,0" x:Name="userControl13" VerticalAlignment="Top" />
    </Grid>
</Window>

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public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    List<UserControl1> ucs = new List<UserControl1>();

    private void Window_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        GetUcsCount(e);
        Console.WriteLine("ucs.Count = {0}", ucs.Count);
    }

    private void GetUcsCount(MouseButtonEventArgs e)
    {
        ucs.Clear();

        Point p = e.GetPosition(this);

        VisualTreeHelper.HitTest(this, null,
            new HitTestResultCallback(MyHitTestCallback),
            new PointHitTestParameters(p));
    }

    HitTestResultBehavior MyHitTestCallback(HitTestResult result)
    {
        if (result.VisualHit.GetType() == typeof(UserControl1))
        {
            ucs.Add(result.VisualHit as UserControl1);
        }

        return HitTestResultBehavior.Continue;
    }
}

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HitTestResultBehavior MyHitTestCallback(HitTestResult result)
{
    DependencyObject visualHit = result.VisualHit;
    UserControl1 parentUserControl = GetVisualParent<UserControl1>(visualHit);
    if (parentUserControl != null && ucs.IndexOf(parentUserControl) < 0)
    {
        ucs.Add(parentUserControl as UserControl1);
    }
    return HitTestResultBehavior.Continue;
}
public static T GetVisualParent< T >(object childObject) where T : Visual
{
    DependencyObject child = childObject as DependencyObject;
    while ((child != null) && !(child is T))
    {
        child = VisualTreeHelper.GetParent(child);
    }
    return child as T;
}