Code

Dim tl As New TreeLayout()

tl.Direction = TreeLayoutDirection.LeftToRight
tl.LayoutNode = New LayoutNode(AddressOf OnLayoutNode)
tl.LinkStyle = TreeLayoutLinkType.Cascading3

nodes = New List(Of DiagramNode)()
tl.Arrange(Diagram1)

nodes.Reverse()

For Each node As DiagramNode In nodes
	Dim c As RectangleF = RectangleF.Empty

	For Each outg As DiagramLink In node.OutgoingLinks

		Dim child As DiagramNode = outg.Destination
		If (c.IsEmpty) Then
			c = child.Bounds
		Else
			c = RectangleF.Union(c, child.Bounds)
		End If

	Next

	If Not c.IsEmpty Then

		Dim b As RectangleF = node.Bounds
		b.Y = c.Top
		node.Bounds = b

	End If

Next
' .........................
Private nodes As List(Of DiagramNode)
Private Sub OnLayoutNode(ByVal node As DiagramNode, ByVal r As RectangleF)
	nodes.Add(node)
End Sub