public static string SyncOutlookToCalDav_EventsExistsInCalDav (string existingEventData, string existingAppointmentId)
    {
      var entityRelationStorage = new EntityRelationStorage<string, DateTime, IEntityRelationData<string, DateTime, Uri, string>, Uri, string>();
      entityRelationStorage.SaveEntityRelationData (new List<IEntityRelationData<string, DateTime, Uri, string>>()
                                                    {
                                                        new OutlookEventRelationData()
                                                        {
                                                            AtypeId = existingAppointmentId,
                                                            AtypeVersion = new DateTime (1),
                                                            BtypeId = new Uri ("/e1", UriKind.Relative),
                                                            BtypeVersion = "v1"
                                                        }
                                                    });

      return SyncOutlookToCalDav_EventsExistsInCalDav (existingEventData, entityRelationStorage);
    }
    public static string SyncCalDavToOutlookAndBackToCalDav (string eventData)
    {
      var entityRelationStorage = new EntityRelationStorage<string, DateTime, IEntityRelationData<string, DateTime, Uri, string>, Uri, string>();

      SyncCalDavToOutlook (eventData, entityRelationStorage);

      var relation = entityRelationStorage.LoadEntityRelationData().First();
      var newRelation = new OutlookEventRelationData()
                        {
                            AtypeId = relation.AtypeId,
                            AtypeVersion = relation.AtypeVersion.AddHours (-1),
                            BtypeId = relation.BtypeId,
                            BtypeVersion = relation.BtypeVersion
                        };
      entityRelationStorage.SaveEntityRelationData (new List<IEntityRelationData<string, DateTime, Uri, string>>() { newRelation });

      return SyncOutlookToCalDav_EventsExistsInCalDav (eventData, entityRelationStorage);
    }