Delete Link, Notify linked nodes

I’ve tried a few different solutions, but I can not manage to notify the connexted nodes / subgraphs. Any help would be appreciated.

You have several options, depending on when you want to get notified and where you want to put the code.
You could implement a GoView.SelectionDeleting event handler that is called just before the selected objects are deleted by the user (via GoView.DeleteSelection, called by GoView.EditDelete or GoView.EditCut). Iterate through the GoView.Selection, find the links that you care about, and then you can refer to the nodes that those links connect.
Or you could implement a GoDocument.Changed event handler, looking for the hint GoLayer.RemovedObject. If the GoChangedEventArgs.GoObject is a link that you care about, you can refer to the nodes that it connects. Note that this event handler will be called even for programmatic object removals, not just when the user deletes an object.
Finally if you want to put the code in your individual classes, you can override GoLink.OnLayerChanged (before you call the base method), or you can override GoPort.OnLinkChanged. You can find examples of these by searching the sample application sources.