添加项目文件。

gong-wpf-dragdrop/src/GongSolutions.WPF.DragDrop/DragAdorner.cs

@@ -0,0 +1,76 @@
+using System.Windows.Documents;
+using System.Windows;
+using System.Windows.Media;
+
+namespace GongSolutions.Wpf.DragDrop
+{
+    internal class DragAdorner : Adorner
+    {
+        public DragAdorner(UIElement adornedElement, UIElement adornment, Point translation, DragDropEffects effects = DragDropEffects.None)
+            : base(adornedElement)
+        {
+            this._translation = translation;
+            this.m_AdornerLayer = AdornerLayer.GetAdornerLayer(adornedElement);
+            this.m_AdornerLayer.Add(this);
+            this.m_Adornment = adornment;
+            this.IsHitTestVisible = false;
+            this.Effects = effects;
+        }
+
+        public DragDropEffects Effects { get; private set; }
+
+        public Point MousePosition
+        {
+            get { return this.m_MousePosition; }
+            set
+            {
+                if (this.m_MousePosition != value)
+                {
+                    this.m_MousePosition = value;
+                    this.m_AdornerLayer.Update(this.AdornedElement);
+                }
+            }
+        }
+
+        public void Detatch()
+        {
+            this.m_AdornerLayer.Remove(this);
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            this.m_Adornment.Arrange(new Rect(finalSize));
+            return finalSize;
+        }
+
+        public override GeneralTransform GetDesiredTransform(GeneralTransform transform)
+        {
+            var result = new GeneralTransformGroup();
+            result.Children.Add(base.GetDesiredTransform(transform));
+            result.Children.Add(new TranslateTransform(this.MousePosition.X + this._translation.X, this.MousePosition.Y + this._translation.Y));
+
+            return result;
+        }
+
+        protected override Visual GetVisualChild(int index)
+        {
+            return this.m_Adornment;
+        }
+
+        protected override Size MeasureOverride(Size constraint)
+        {
+            this.m_Adornment.Measure(constraint);
+            return this.m_Adornment.DesiredSize;
+        }
+
+        protected override int VisualChildrenCount
+        {
+            get { return 1; }
+        }
+
+        private readonly AdornerLayer m_AdornerLayer;
+        private readonly UIElement m_Adornment;
+        private Point m_MousePosition;
+        private Point _translation;
+    }
+}