Overview
A TreeView control is made up of a hierarchical structure of tree nodes. It
inherits from BaseNavigator and
shares the same concept of other navigation controls. Below is a picture of the
built-in Explorer_WithCheckBox TreeView:

In order to design the appearance setting, you need to understand the
difference between a TreeNode and a TreeNodeGroup so that you can decide proper
CSS style settings on TreeNode and TreeNodeGroup.
TreeNode and TreeNodeGroup
A TreeNode can contain any of the
following elements:
-
An optional image associate with this TreeNode, represented by
ImageUrl
property;
-
An optional Checkbox displayed between the image and the TreeNode text,
represented by TreeView's CheckBoxImages
property.
-
Text as the main content of the TreeView, represented by TreeNode's
Text property
TreeNode can have different states. See
TreeNode
topic for more details.
A TreeNodeGroup contains several
TreeNodes. Below shows the area of TreeNode and TreeNodeGroup.
Using TreeView and MultiPage
To associate a TreeView with MultiPage, simply specify the
MultiPageID property for the TreeView. By default, TreeNode
automatically associates with the page view.
For example, setting TreeView1.MultiPageID to "MultiPage1" tells the TreeView
to switch PageViews on MultiPage1. When user clicks on the first tab item, the
first PageView of the MultiPage appears.
To explicitly associate a TreeNode with a PageView, set
PageViewID to the ID of the PageView.