WPF 图层管理

玩过phtoshop或者blend的人都知道里面都一个图层管理器，管理图层的遮挡顺序，有置顶层、置底层、置下一层、置上一层四个管理方式。

那么在wof中我们应该怎么玩呢? 请看代码，支持多个图层同时操作。

首先置顶：

  private void BringToFront(List<UIElement> CurrentSelection ,UIElementCollection childrens)
        {
            List<UIElement> selectionSorted = (from item in CurrentSelection
                                               orderby Canvas.GetZIndex(item as UIElement) ascending
                                               select item as UIElement).ToList();

            List<UIElement> childrenSorted = (from UIElement item in childrens
                                              orderby Canvas.GetZIndex(item as UIElement) ascending
                                              select item as UIElement).ToList();

            int i = 0;
            int j = 0;
            foreach (UIElement item in childrenSorted)
            {
                if (selectionSorted.Contains(item))
                {
                    int idx = Canvas.GetZIndex(item);
                    Canvas.SetZIndex(item, childrenSorted.Count - selectionSorted.Count + j++);
                }
                else
                {
                    Canvas.SetZIndex(item, i++);
                }
            }
        }

置底类似：

   private void SendToBack(List<UIElement> CurrentSelection ,UIElementCollection childrens)
        {
            List<UIElement> selectionSorted = (from item in CurrentSelection
                                               orderby Canvas.GetZIndex(item as UIElement) ascending
                                               select item as UIElement).ToList();

            List<UIElement> childrenSorted = (from UIElement item in childrens

                                              orderby Canvas.GetZIndex(item as UIElement) ascending
                                              select item as UIElement).ToList();
            int i = 0;
            int j = 0;
            foreach (UIElement item in childrenSorted)
            {
                if (selectionSorted.Contains(item))
                {
                    int idx = Canvas.GetZIndex(item);
                    Canvas.SetZIndex(item, j++);

                }
                else
                {
                    Canvas.SetZIndex(item, selectionSorted.Count + i++);
                }
            }
        }        

　置下一层：

 private void SendBackward(List<UIElement> CurrentSelection ,UIElementCollection childrens)

        {
            List<UIElement> ordered = (from item in CurrentSelection
                                       orderby Canvas.GetZIndex(item as UIElement) ascending
                                       select item as UIElement).ToList();

            int count = childrens.Count;

            for (int i = 0; i < ordered.Count; i++)
            {
                int currentIndex = Canvas.GetZIndex(ordered[i]);
                int newIndex = Math.Max(i, currentIndex - 1);
                if (currentIndex != newIndex)
                {
                    Canvas.SetZIndex(ordered[i], newIndex);
                    IEnumerable<UIElement> it =childrens.OfType<UIElement>().Where(item => Canvas.GetZIndex(item) == newIndex);

                    foreach (UIElement elm in it)
                    {
                        if (elm != ordered[i])
                        {
                            Canvas.SetZIndex(elm, currentIndex);
                            break;
                        }
                    }
                }
            }
        }

　置上一层：

  private void BringForward(List<UIElement> CurrentSelection ,UIElementCollection childrens)

        {
            List<UIElement> ordered = (from item in CurrentSelection
                                       orderby Canvas.GetZIndex(item as UIElement) descending
                                       select item as UIElement).ToList();

            int count = childrens.Count;

            for (int i = 0; i < ordered.Count; i++)
            {
                int currentIndex = Canvas.GetZIndex(ordered[i]);
                int newIndex = Math.Min(count - 1 - i, currentIndex + 1);
                if (currentIndex != newIndex)
                {
                    Canvas.SetZIndex(ordered[i], newIndex);
                    IEnumerable<UIElement> it = this.Children.OfType<UIElement>().Where(item => Canvas.GetZIndex(item) == newIndex);

                    foreach (UIElement elm in it)
                    {
                        if (elm != ordered[i])
                        {
                            Canvas.SetZIndex(elm, currentIndex);
                            break;
                        }
                    }
                }
            }
        }