You can use XmlDataSource
as Jeremy suggested or change code as below
XElement doc = XElement.Load("~/App_Data/test_xml.xml");
TreeNode root = new TreeNode("FEATURES");
foreach (XElement state in doc.Descendants("FEATURE"))
{
TreeNode feature = new TreeNode(state.Attribute("NAME").Value);
foreach (XElement region in state.Descendants("USER"))
{
TreeNode user = new TreeNode(region.Attribute("NAME").Value);
foreach (XElement area in region.Descendants("NAME"))
{
user.ChildNodes.Add(new TreeNode(area.Attribute("NAME").Value));
}
feature.ChildNodes.Add(user);
}
root.ChildNodes.Add(feature);
}
treeview.Nodes.Add(root);