Hi malobaili,

Please refer below articles

Bind and display hierarchical data with TreeView in ASP.Net using C# and VB.Net

http://www.aspforums.net/Threads/110940/How-to-bind-TreeView-control-from-database-in-ASPNet/

Here I have created sample.

HTML

<div>
    <h3>
        User Details</h3>
    <hr />
    <asp:TreeView ID="TreeView1" runat="server" ImageSet="News" NodeIndent="15">
        <HoverNodeStyle Font-Underline="True" ForeColor="#6666AA" />
        <NodeStyle Font-Names="Tahoma" Font-Size="8pt" ForeColor="Black" HorizontalPadding="2px"
            NodeSpacing="0px" VerticalPadding="2px"></NodeStyle>
        <ParentNodeStyle Font-Bold="False" />
        <SelectedNodeStyle BackColor="#B5B5B5" Font-Underline="False" HorizontalPadding="0px"
            VerticalPadding="0px" />
    </asp:TreeView>
</div>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = this.GetData("SELECT Ma_Phong, TenPhong FROM TB_PhongBan");
        this.PopulateTreeView(dt, string.Empty, null);
    }
}

private void PopulateTreeView(DataTable dtParent, string parentId, TreeNode treeNode)
{
    foreach (DataRow row in dtParent.Rows)
    {
        TreeNode child = new TreeNode
        {
            Text = row[1].ToString(),
            Value = row[0].ToString()
        };
        if (string.IsNullOrEmpty(parentId))
        {
            TreeView1.Nodes.Add(child);
            DataTable dtChild = this.GetData("SELECT MaPhong, HoVaTen FROM TB_User WHERE MaPhong ='" + child.Value + "'");
            PopulateTreeView(dtChild, child.Value, child);
        }
        else
        {
            treeNode.ChildNodes.Add(child);
        }
    }
}

private DataTable GetData(string query)
{
    DataTable dt = new DataTable();
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand(query))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.CommandType = CommandType.Text;
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                sda.Fill(dt);
            }
        }
        return dt;
    }
}

Screenshot

I hope this will help you out.