WPF ListBox控件鼠标拖拽MVVM设计

1.利用ListBox控件的两个事件：PreviewMouseMove、Drop

2.数据交换过程中的排序

#region 拖拽


        public RelayCommand<MouseEventArgs> PreviewMouseMoveCommand => new RelayCommand<MouseEventArgs>(ExecutePreviewMouseMoveCommand);

        public RelayCommand<DragEventArgs> DropCommand => new RelayCommand<DragEventArgs>(ExecuteDropCommand);

        private void ExecutePreviewMouseMoveCommand(MouseEventArgs e)
        {
            ListBox_PreviewMouseMove(e);
        }
        private void ExecuteDropCommand(DragEventArgs e)
        {
            ListBox_Drop(e);
        }


        private Point _dragStartPoint;

        private T FindVisualParent<T>(DependencyObject child)
            where T : DependencyObject
        {
            var parentObject = VisualTreeHelper.GetParent(child);
            if (parentObject == null)
                return null;
            T parent = parentObject as T;
            if (parent != null)
                return parent;
            return FindVisualParent<T>(parentObject);
        }

        private void ListBox_PreviewMouseMove(MouseEventArgs e)
        {
            Point point = e.GetPosition(null);
            Vector diff = _dragStartPoint - point;
            if (e.LeftButton == MouseButtonState.Pressed &&
                (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance ||
                    Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance))
            {
                //var lb = sender as ListBox;
                var lbi = FindVisualParent<ListBoxItem>(((DependencyObject)e.OriginalSource));
                var lbi2 = FindVisualParent<ListBoxItem>(((DependencyObject)e.Source));
                if (lbi != null)
                {
                    DragDrop.DoDragDrop(lbi, lbi.DataContext, DragDropEffects.Move);
                }
            }
        }

        private void ListBox_Drop(DragEventArgs e)
        {

            var source = e.Data.GetData(typeof(MainModel)) as MainModel;
            //var target = e.OriginalSource;
            var lbi = FindVisualParent<ListBoxItem>(((DependencyObject)e.OriginalSource));
            var target = lbi.DataContext as MainModel;
            int i = 0;
            //var listBox = sender as ListBox;
            //int sourceIndex = listBox.Items.IndexOf(source);
            //int targetIndex = listBox.Items.IndexOf(target);

            //Move(source, sourceIndex, targetIndex);

            int sourceIndex = Models.IndexOf(source);
            int targetIndex = Models.IndexOf(target);

            //Move(source, sourceIndex, targetIndex);
            Displace(source,target);
        }

        private void Move(MainModel source, int sourceIndex, int targetIndex)
        {
            if (sourceIndex < targetIndex)
            {
                _models.Insert(targetIndex + 1, source);
                _models.RemoveAt(sourceIndex);
            }
            else
            {
                int removeIndex = sourceIndex + 1;
                if (_models.Count + 1 > removeIndex)
                {
                    _models.Insert(targetIndex, source);
                    _models.RemoveAt(removeIndex);
                }
            }
        }

        private void Displace(MainModel source, MainModel target)
        {
            int sourceIndex = Models.IndexOf(source);
            int targetIndex = Models.IndexOf(target);
            var s = source.Clone;
            var t = target.Clone;
            //Models.Move(sourceIndex,targetIndex);
            Models.Displace0(sourceIndex,targetIndex);
        }

      
        #endregion

3.置换数据扩展方法

 /// <summary>
        /// 置换数据
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        /// <param name="oldIndex">原数据索引</param>
        /// <param name="newIndex">新数据索引</param>
        /// <returns></returns>
        public static bool Displace<T>(this ObservableCollection<T> list, int oldIndex, int newIndex)
        {
            if (oldIndex >= list.Count || newIndex >= list.Count || oldIndex < 0 || newIndex < 0 || oldIndex == newIndex) { return false; }
            try
            {
                var sel = list[oldIndex];
                list[oldIndex] = list[newIndex];
                list[newIndex] = sel;
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }