WPF拖放按钮

我正在编写一个具有按钮网格的WPF应用程序，我希望允许用户在网格之间拖放按钮，可能在应用程序的不同实例之间。我试过通过在按钮上添加一个处理程序到PreviewMouseMove事件，然后调用DoDragDrop，如果鼠标左键是下的，但是当我拖放按钮时，它总是以两次调用DoDragDrop和两次拖放事件处理程序结束。有人知道为什么会发生这种情况以及如何预防吗?

下面是一些演示问题的示例XAML:

<Window x:Class="WpfTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <DockPanel>
        <Button PreviewMouseMove="PreviewMouseMove" x:Name="m_button" Width="250">
            Hello, world!
        </Button>
        <Label Drop="Drop" AllowDrop="True">
            Drop here!
        </Label>
    </DockPanel>
</Window>

和相应的代码:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }
    private void PreviewMouseMove(object sender, MouseEventArgs e)
    {
        if (e.LeftButton == MouseButtonState.Pressed)
        {
            ++m_dragIndex;
            System.Console.WriteLine("Dragged: " + m_dragIndex.ToString());
            DragDrop.DoDragDrop(m_button, m_dragIndex, DragDropEffects.All);
            e.Handled = true;
        }
    }
    private void Drop(object sender, DragEventArgs e)
    {
        System.Console.WriteLine("Dropped: " + e.Data.GetData(typeof(Int32)).ToString());
    }
    private int m_dragIndex;
}

对于单个拖动，它被写入输出:

Dragged: 1
Dragged: 2
Dropped: 2
Dropped: 1

UPDATE:我已经更改了上面的示例代码，以显示当按钮被放置到某些东西上时调用哪些放置事件。

UPDATE:更新了问题，包括容器和应用程序实例之间的拖拽，因为这是使用拖拽系统的激励因素

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }
    private void PreviewMouseMove(object sender, MouseEventArgs e)
    {
        if(!m_inMouseMove)
        {
            m_inMouseMove = true;
            if (e.LeftButton == MouseButtonState.Pressed)
            {
                ++m_dragIndex;
                System.Console.WriteLine("Dragged: " + m_dragIndex.ToString());
                DragDrop.DoDragDrop(m_button, m_dragIndex, DragDropEffects.All);
                e.Handled = true;
            }
            m_inMouseMove = false;
        }
    }
    private void Drop(object sender, DragEventArgs e)
    {
        System.Console.WriteLine("Dropped: " + e.Data.GetData(typeof(Int32)).ToString());
    }
    private int m_dragIndex;
    bool m_inMouseMove;
}