public FollowManagePageViewModel(
            ApplicationLayoutManager applicationLayoutManager,
            PageManager pageManager,
            NiconicoSession niconicoSession,
            FollowManager followManager
            )
        {
            ApplicationLayoutManager = applicationLayoutManager;
            PageManager     = pageManager;
            NiconicoSession = niconicoSession;
            FollowManager   = followManager;

            NowUpdatingFavList = new ReactiveProperty <bool>();

            UpdateFavListCommand = new DelegateCommand <IFollowInfoGroup>(async(group) =>
            {
                NowUpdatingFavList.Value = true;
                try
                {
                    await FollowManager.SyncAll();
                }
                catch
                {
                    Debug.WriteLine($"{group.FollowItemType} のFollow List更新に失敗");
                }
                finally
                {
                    NowUpdatingFavList.Value = false;
                }
            });


            FollowGroups = new ObservableCollection <IFollowInfoGroup>()
            {
                FollowManager.User,
                FollowManager.Mylist,
                FollowManager.Tag,
                FollowManager.Community,
                FollowManager.Channel,
            };
        }