TreeView node = new TreeView();
string selectedVaule= node.SelectedValue ; //gets the value of the selected node
建议参考下这个页面,可以更深入的了解:
http://msdn.microsoft.com/zh-cn/library/system.web.ui.webcontrols.treenode.aspx
TreeView.SelectedNode.Value
or
TreeView.SelectedValue
treeview1.SelectedValue