internal static void AddNonMailFolderToSharedFoldersGroup(UserContext userContext, Folder folder, NavigationNodeGroupSection groupSection) { if (groupSection == NavigationNodeGroupSection.Mail) { throw new ArgumentOutOfRangeException("Cannot add mail folder to shared folder group"); } NavigationNodeCollection navigationNodeCollection = NavigationNodeCollection.TryCreateNavigationNodeCollection(userContext, userContext.MailboxSession, groupSection); if (navigationNodeCollection.FindFoldersById(folder.Id.ObjectId).Length == 0) { navigationNodeCollection.AddFolderToDefaultGroup(userContext, NavigationNodeGroupType.SharedFoldersGroup, folder, true); navigationNodeCollection.Save(userContext.MailboxSession); } }