Hi,

There are no special annotation objects in the library. You could use ShapeNodes for that, and set their AllowIncoming / AllowOutgoingLinks properties to false in order to prevent users from drawing links to the annotations. So adding an annotation when the diagram is clicked could look like this:

private void OnDiagramClicked(object sender, DiagramEventArgs e)
{
	if (e.MouseButton == MouseButton.Left)
	{
		var rect = new Rect(e.MousePosition, new Size(0, 0));
		rect.Inflate(40, 30);
		var annotation = diagram.Factory.CreateShapeNode(rect);
		diagram.BeginEdit(annotation);
	}
} 

Tree and Flowchart layouts are shown in the following samples: DirTree, JavaScript, TreeLayout. In addition, the custom layout code shown in WorkflowDesigner is what later became FlowchartLayout - you could use it as a base of your custom layout class to add support for more types of code statements.

I hope that helps,
Stoyan