WPF列表框拖放是否与上下文菜单冲突?

我正在从列表框中实现拖放,但我看到了一些奇怪的行为,窗口中的其他地方有一个ContextMenu。如果打开上下文菜单,然后从列表框中开始拖动,则上下文菜单将关闭,但在执行另一次拖动之前不会再次打开。

这有道理吗?有人知道会发生什么事吗?

<ListBox Grid.Row="0" ItemsSource="{Binding SourceItems}" MultiSelectListboxDragDrop:ListBoxExtension.SelectedItemsSource="{Binding SelectedItems}" SelectionMode="Multiple" PreviewMouseLeftButtonDown="HandleLeftButtonDown" PreviewMouseLeftButtonUp="HandleLeftButtonUp" PreviewMouseMove="HandleMouseMove"/>
<ListBox Grid.Row="1" ItemsSource="{Binding DestinationItems}" AllowDrop="True" Drop="DropOnToDestination" />
<Button Grid.Row="2">
    <Button.ContextMenu>
        <ContextMenu x:Name="theContextMenu">
            <MenuItem Header="context 1"/>
            <MenuItem Header="context 2"/>
            <MenuItem Header="context 3"/>
        </ContextMenu>
    </Button.ContextMenu>
    Button with context menu
</Button>

…

public partial class Window1
{
    private bool clickedOnSourceItem;

    public Window1()
    {
        InitializeComponent();

        DataContext = new WindowViewModel();
    }

    private void DropOnToDestination(object sender, DragEventArgs e)
    {
        var viewModel = (WindowViewModel)e.Data.GetData(typeof(WindowViewModel));
        viewModel.CopySelectedItems();
    }

    private void HandleLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        var sourceElement = (FrameworkElement)sender;
        var hitItem = sourceElement.InputHitTest(e.GetPosition(sourceElement)) as FrameworkElement;

        if(hitItem != null)
        {
            clickedOnSourceItem = true;
        }
    }

    private void HandleLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        clickedOnSourceItem = false;
    }

    private void HandleMouseMove(object sender, MouseEventArgs e)
    {
        if(clickedOnSourceItem)
        {
            var sourceItems = (FrameworkElement)sender;
            var viewModel = (WindowViewModel)DataContext;

            DragDrop.DoDragDrop(sourceItems, viewModel, DragDropEffects.Move);
            clickedOnSourceItem = false;
        }
    }
}