Treeview 控件的精通使用，用其生成树，同时将要保存的节点，保存到list然后，将其清空，点击回显后，让其从新选中。-Proficiency in the use of the Treeview control, using the spanning tree, at the same time to preserve the node, and then save it to list its empty, click back significantly after the re-select them.