Create IOvalUIModel

Plug-in & Open API
1

Hello,

I try to create IOvalUIModel:

DiagramManager diagramManager = ApplicationManager.instance().getDiagramManager();
IDiagramUIModel diagram = ... //
IModelElement oval = IModelElementFactory.instance().createOval();
IDiagramElement ovalDiagramElement = diagramManager.createDiagramElement(diagram, oval);
IOvalUIModel eventDE = (IOvalUIModel)ovalDiagramElement;

Method createDiagramElement() return null.
What’s wrong with that code? Any help is appreciated.

Thank you in advance.
anita