GoLayout with custom classes

GoLayout doesn’t seems to work with class I’m creating that inherits another class.
Even the following simple class doesn’t work with GoLayout.
public class GoTextWithToolTip : GoText
the Form is using the following code for the layout:
private void button3_Click(object sender, EventArgs e)
GoLayoutLayeredDigraph _Layout = new GoLayoutLayeredDigraph();
_Layout.Document = goView1.Document;
_Layout.Network = null;
_Layout.DirectionOption = GoLayoutDirection.Right;
_Layout.LayeringOption = GoLayoutLayeredDigraphLayering.LongestPathSource;
_Layout.InitializeOption = GoLayoutLayeredDigraphInitIndices.DepthFirstIn;
What am I doing wrong?

Hmmm, this message looks familiar.
Your button3_click code looks fine. (Although if you want to support undo/redo, you need to put a StartTransaction/FinishTransaction around that code.)
What is in your document? GoLayout expects to work with a graph of nodes and links. If your top-level objects are GoText objects (or instances of any subclass of GoText, or GoShape, or GoImage et al.), then GoLayout will just ignore those, since they clearly aren’t part of any graph.