IFeatureProvider featureProvider;
	IPeService peService;

	public Collection<Diagram> getLinkedDiagrams(PictogramElement pe,
			boolean createOnDemand) {
		final Diagram currentDiagram = featureProvider.getDiagramTypeProvider()
				.getDiagram();
		final Collection<Diagram> diagrams = new HashSet<Diagram>();

		final Object[] businessObjectsForPictogramElement = featureProvider
				.getAllBusinessObjectsForPictogramElement(pe);
		String firstID = null;
		for (Object bo : businessObjectsForPictogramElement) {
			firstID = getIDOfBusinessObject(bo);
			if (firstID != null) break;
		}
		if (firstID != null) {
			String diagramId = "diagram_" + firstID;

			EObject linkedDiagram = null;
			for (TreeIterator<EObject> i = EcoreUtil.getAllProperContents(
					currentDiagram.eResource().getContents(), false); i
					.hasNext();) {
				EObject eObject = i.next();
				if (eObject instanceof Diagram) {
					if (diagramId.equals(((Diagram) eObject).getName())) {
						linkedDiagram = eObject;
						break;
					}
				}
			}

			if (!(linkedDiagram instanceof Diagram)) {
				if (createOnDemand) {
					Diagram newDiagram = peService.createDiagram(
							currentDiagram.getDiagramTypeId(), diagramId,
							currentDiagram.isSnapToGrid());
					currentDiagram.eResource().getContents().add(newDiagram);

					linkedDiagram = newDiagram;
				} else {
					return diagrams;
				}
			}

			if (!EcoreUtil.equals(currentDiagram, linkedDiagram)) {
				diagrams.add((Diagram) linkedDiagram);
			}
		}

		return diagrams;
	}

	public void execute(ICustomContext context) {
		final PictogramElement pe = context.getPictogramElements()[0];
		final Collection<Diagram> possibleDiagramsList = getLinkedDiagrams(pe, true);

		if (!possibleDiagramsList.isEmpty()) {
			final Diagram[] possibleDiagrams = possibleDiagramsList
					.toArray(new Diagram[0]);
			if (possibleDiagramsList.size() == 1) {
				final Diagram diagram = possibleDiagrams[0];
				openDiagram(context, diagram);
			} else {
				ListDialog dialog = new ListDialog(PlatformUI.getWorkbench()
						.getActiveWorkbenchWindow().getShell());
				dialog.setContentProvider(new IStructuredContentProvider() {

					@Override
					public void dispose() {
					}

					@Override
					public Object[] getElements(Object inputElement) {
						return possibleDiagramsList.toArray();
					}

					@Override
					public void inputChanged(Viewer viewer, Object oldInput,
							Object newInput) {
					}
				});
				dialog.setTitle("Choose Diagram");
				dialog.setMessage("Choose Diagram to open");
				dialog.setInitialSelections(new Diagram[] { possibleDiagrams[0] });
				dialog.setLabelProvider(new DiagramLabelProvider());
				dialog.setAddCancelButton(true);
				dialog.setHelpAvailable(false);
				dialog.setInput(new Object());
				dialog.open();
				Object[] result = dialog.getResult();
				if (result != null) {
					for (int i = 0; i < result.length; i++) {
						Diagram diagram = (Diagram) result[i];
						openDiagram(context, diagram);
					}
				}
			}
		}
	}

	protected void openDiagram(ICustomContext context, Diagram diagram) {
		openDiagramEditor(diagram,
				getDiagramEditor().getEditingDomain(),
				getFeatureProvider().getDiagramTypeProvider().getProviderId(),
				false);
	}

getDiagram().eResource().getContents().add(addedClass);