Hi Jack,

I'm glad that you like the products!

I would recommend you to use manual load on demand for that case, here is a short sample which you can use as a starting point:

<form id="form1" runat="server">
 <asp:ScriptManager ID="ScriptManager1" runat="server">
 </asp:ScriptManager>
 <ig:WebDataTree ID="WebDataTree1" runat="server" Height="300px" Width="200px">
 </ig:WebDataTree>
</form>

And code behind:

Imports System.IO
Imports Infragistics.Web.UI.NavigationControls

Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not IsPostBack Then
            PopulateDirectory(WebDataTree1.Nodes, Server.MapPath("~/"))
        End If
    End Sub

    Protected Sub WebDataTree1_NodePopulate(ByVal sender As Object, ByVal e As Infragistics.Web.UI.NavigationControls.DataTreeNodeEventArgs) Handles WebDataTree1.NodePopulate
        PopulateDirectory(e.Node.Nodes, e.Node.DataPath)
    End Sub

    Sub PopulateDirectory(ByVal nodes As DataTreeNodeCollection, ByVal path As String)
        Dim info As DirectoryInfo
        info = New DirectoryInfo(path)

        For Each dir As DirectoryInfo In info.GetDirectories()
            Dim folderNode As DataTreeNode
            folderNode = New DataTreeNode()
            folderNode.Text = dir.Name
            folderNode.DataPath = String.Format("{0}/{1}", path, dir.Name)
            folderNode.IsEmptyParent = dir.GetDirectories().Length > 0
            nodes.Add(folderNode)
        Next
    End Sub
End Class

Hope that helps!