WPF中沒有提供確保顯示TreeView選中的Item的功能，因此寫個函式實現：

        public void EnsureTreeViewItemVisible(TreeView treeview, TreeViewItem selectedItem)
        {
            Point itemPosition = selectedItem.TranslatePoint(new Point(0, 0), treeview);

            ScrollViewer scrollViewer = (ScrollViewer)VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(treeview, 0), 0);

            int childenCount = VisualTreeHelper.GetChildrenCount(selectedItem);

            double selectdItemWidth = treeview.ActualWidth;
            double selecedItemHeight = 16;

            if (childenCount > 0)
            {
                FrameworkElement itemGrid = (FrameworkElement)VisualTreeHelper.GetChild(selectedItem, 0);

                FrameworkElement itemExpander = (FrameworkElement)VisualTreeHelper.GetChild(itemGrid, 0);

                FrameworkElement itemBorder = (FrameworkElement)VisualTreeHelper.GetChild(itemGrid, 1);

                selectdItemWidth = itemExpander.ActualWidth + itemBorder.ActualWidth;
                selecedItemHeight = itemBorder.ActualHeight > itemExpander.ActualHeight ? itemBorder.ActualHeight : itemExpander.ActualHeight;
            }
            else
            {
                Trace.WriteLine("Can't get the item children!");
            }

            double horizontalOffset = scrollViewer.HorizontalOffset;
            if (itemPosition.X < 0)
            {
                horizontalOffset += itemPosition.X;
            }
            else if ((itemPosition.X + selectdItemWidth) > scrollViewer.ViewportWidth)
            {
                if (selectdItemWidth > treeview.ActualWidth)
                {
                    horizontalOffset -= itemPosition.X;
                }
                else
                {
                    horizontalOffset += (itemPosition.X + selectdItemWidth - scrollViewer.ViewportWidth);
                }
            }

            if (horizontalOffset != scrollViewer.HorizontalOffset)
                scrollViewer.ScrollToHorizontalOffset(horizontalOffset);

            double verticalOffset = scrollViewer.VerticalOffset;
            if (itemPosition.Y < 0)
            {
                verticalOffset += itemPosition.Y;
            }
            else if ((itemPosition.Y + selecedItemHeight) > scrollViewer.ViewportHeight)
            {
                verticalOffset += (itemPosition.Y + selecedItemHeight - scrollViewer.ViewportHeight);
            }

            if (verticalOffset != scrollViewer.VerticalOffset)
                scrollViewer.ScrollToVerticalOffset(verticalOffset);

        }

        private void TestTreeView_ItemSelected(object sender, RoutedEventArgs e)
        {
            Application.Current.Dispatcher.BeginInvoke(new Action(delegate
                {
                    TreeViewItem selectedItem = e.OriginalSource as TreeViewItem;

                    ViewModel.EnsureTreeViewItemVisible(VisualElementTree, selectedItem);

                }), System.Windows.Threading.DispatcherPriority.ApplicationIdle);
        }

        <TreeView x:Name="TestTreeView" TreeViewItem.Selected="TestTreeView_ItemSelected">
          </TreeView>