public void doSave(IProgressMonitor monitor) {
try {
   for (int i = 0; i < diag.getLink().getBusinessObjects().size(); i++) {
	EObject eobj =  diag.getLink().getBusinessObjects().get(i);
				
	if(eobj instanceof Task){
	   Task task = (Task) eobj;
					 
	   if(task.getMcTaskId() == null){
	     task.setMcTaskId(/*ID received from database*/);
	   }
	  }
    }
} catch (RuntimeException e) {
   e.printStackTrace();
}