The control is perfect for implementing hierarchical structures in a User Interface, and this code will show you how to actually get the data into the control from a 'parent-child' database table. This code makes use of a recursive function.
You can read a step-by-step explanation in a tutorial I wrote.
<%@ Page Language="C#" CompileWith="tree.aspx.cs" ClassName="tree_aspx" Debug="true" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" " http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Select item from treeview</title>
</head>
<body>
<form id="form1" runat="server">
<asp:TreeView ID="EmployeeList" Runat="Server" />
</form>
</body>
</html>
and the code-behind
using System;
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Configuration;
using System.Web;
using System.Web.Caching;
using System.Web.Security ;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
DataSet EmployeeDS = new DataSet();
void page_load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
// first load DataSet
LoadDataSet();
// now build list
BuildEmployeeList(EmployeeList.Nodes, 0);
}
}
void LoadDataSet()
{
String conn = ConfigurationSettings.AppSettings["connStr"];
String strSQL = "SELECT id, name, mgr_id FROM [employees]";
SqlDataAdapter myAdapter = new SqlDataAdapter(strSQL, conn);
myAdapter.Fill(EmployeeDS, "employees");
}
private void BuildEmployeeList(TreeNodeCollection nodes, Int32 IntParent)
{
Int32 ThisID;
String ThisName;
DataRow[] children = EmployeeDS.Tables["employees"].Select("mgr_id='"+IntParent+"'");
//no child nodes, exit function
if (children.Length == 0) return;
foreach (DataRow child in children)
{
ThisID = Convert.ToInt32(child.ItemArray[0]);
ThisName = Convert.ToString(child.ItemArray[1]);
TreeNode NewNode = new TreeNode(ThisName, ThisID.ToString());
nodes.Add(NewNode);
NewNode.ToggleExpandState();
BuildEmployeeList(NewNode.ChildNodes, ThisID);
}
}
