wpf 拖拽有阴影效果

using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;

namespace WpfApp37
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private AdornerLayer mAdornerLayer;
        private DragDropAdorner adorner;

        public MainWindow()
        {
            InitializeComponent();

        }

        private void UIElement_OnPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            if (sender is Border bd)
            {
                bd.CaptureMouse();
                //  DragDrop.DoDragDrop(bb, "", DragDropEffects.Copy);
            }
        }

        private void UIElement_OnMouseMove(object sender, MouseEventArgs e)
        {
            var pos = e.GetPosition(this);
            Console.WriteLine("move:" + pos.X + pos.Y);
            if (sender is Border bd)
            {
                Console.WriteLine("move0000000------000");

                if (bd.IsMouseCaptured)
                {
                    Move();

                }



            }
        }

        private void Move()
        { 
            adorner = new DragDropAdorner(tb);
            adorner.IsHitTestVisible = false;
            mAdornerLayer = AdornerLayer.GetAdornerLayer(cv);
            mAdornerLayer.IsHitTestVisible = false;
            mAdornerLayer.Add(adorner);

            DragDrop.DoDragDrop(tb, "", DragDropEffects.Copy);

            mAdornerLayer.Remove(adorner);
            mAdornerLayer = null;
        }

        private void UIElement_OnDragEnter(object sender, DragEventArgs e)
        {

        }

        private void UIElement_OnDragOver(object sender, DragEventArgs e)
        {

            e.Effects = DragDropEffects.Move | DragDropEffects.Copy;
        }

        private void MainWindow_OnLoaded(object sender, RoutedEventArgs e)
        {

        }

        private void Bb_OnPreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if (sender is Border bd)
            {
                bd.ReleaseMouseCapture();
                //  DragDrop.DoDragDrop(bb, "", DragDropEffects.Copy);
            }
        }

        private int i = 0;
        private void Bb_OnQueryContinueDrag(object sender, QueryContinueDragEventArgs e)
        {
            if (e.KeyStates==(DragDropKeyStates.LeftMouseButton|DragDropKeyStates.AltKey) )
            {
                e.Action = DragAction.Cancel;
                 e.Handled = true;
            }
            mAdornerLayer.Update();
            i++;
            Console.WriteLine("update   "+i);
        }
    }


    public class DragDropAdorner : Adorner
    {
        public Brush CustomBrush = null;
        public DragDropAdorner(UIElement parent)
            : base(parent)
        {
            IsHitTestVisible = false;
            mDraggedElement = parent as FrameworkElement;
        }



        protected override void OnRender(DrawingContext drawingContext)
        {
            base.OnRender(drawingContext);
            Console.WriteLine("Render///");
            if (mDraggedElement != null)
            {
                Win32.POINT screenPos = new Win32.POINT();
                if (Win32.GetCursorPos(ref screenPos))
                {
                    Point pos = PointFromScreen(new Point(screenPos.X, screenPos.Y));
                    Rect rect = new Rect(pos.X, pos.Y, mDraggedElement.ActualWidth, mDraggedElement.ActualHeight);

                    drawingContext.PushOpacity(1.0);
                    Brush highlight = null;
                    if (CustomBrush == null)
                    {
                        highlight = mDraggedElement.TryFindResource(SystemColors.HighlightBrushKey) as Brush;
                    }
                    else
                    {
                        highlight = CustomBrush;
                    }
                    if (highlight != null)
                    {
                        drawingContext.DrawRectangle(highlight, new Pen(Brushes.Transparent, 0), rect);
                    }

                    Console.WriteLine($"{rect.X},{rect.Y},{rect.Width},{rect.Height}");
                    drawingContext.DrawRectangle(new VisualBrush(mDraggedElement),
                        new Pen(Brushes.Transparent, 0), rect);
                    drawingContext.Pop();
                }
                else
                {
                    Console.WriteLine("false");
                }
            }
        }

        private FrameworkElement mDraggedElement = null;
    }
    public static class Win32
    {
        public struct POINT { public Int32 X; public Int32 Y; }

        [DllImport("user32.dll")]
        public static extern bool GetCursorPos(ref POINT point);
    }
}