I have a CustomDiagramLink, subclass of DiagramLink, I can save it through SaveToXml, but when I load I get a InvalidOperationException exception.
Here is written (Point 5) that I should call RegisterItemClass on the diagram
http://www.mindfusion.eu/onlinehelp/flowchartnet/Serialization_of_FlowChart_NET_...
But the Diagram class does not look to have RegisterItemClass

Here is written that a parameter-less constructor (or one with a diagram parameter) should be provided by the custom class.
http://www.mindfusion.eu/onlinehelp/flowchartnet/M_MindFusion_Diagramming_Diagra...
So, I have built a constructor with only a diagram parameter, and things seem to work. But is it correct?
Also, while the saved diagram could display proper arrowheads, the diagram loaded from a file does not show the arrowheads, even if I add this feature after loading the diagram from file!
(I do:
Diagram.LinkBaseShape = MindFusion.Diagramming.Wpf.ArrowHeads.Arrow;

and - even if it should not be necessary - in each link:
this.HeadShape = MindFusion.Diagramming.Wpf.ArrowHeads.Arrow;
)
What could I do?

I have none of these problems with Node's subclasses.

Yes, this example solved my problems
http://mindfusion.eu/Forum/YaBB.pl?num=1498704395
(even if I still had to create a CustomLink constructor with only the diagram as parameter - but this looks reasonable)

Thank you!