C# ReactiveCommand.Where方法代码示例

        public MetroiLinksViewModel()
        {
            OpenPageSelectorCommand = new ReactiveCommand();
            OpenPageSelectorCommand
                .Where(x => MetroiLink != null)
                .Select(x => new Dialog.PageSelector())
                .Subscribe(x =>
                {
                    x.Show();
                    MessageBus.Current.SendMessage(CommunityProfiles, "pagesToSelect");
                });

            this.ObservableForProperty(x => x.MetroiLink)
                .Subscribe(x =>
                {
                    ShowEditor = x.Value != null;
                    NotShowEditor = !ShowEditor;
                    var cpRepo = new CommunityProfilesRepo();
                    if (x.Value != null)
                        CommunityProfiles = new ReactiveList<Page>(cpRepo.GetCommunityProfiles(x.Value.Client_ID));
                });

            CommunityProfiles = new ReactiveList<Page>();
            NotShowEditor = !ShowEditor;
        }

        public NowPlayingViewModel()
        {
            _playbackController = IoC.Get<PlaybackController>();

            SelectionChangedCommand = new ReactiveCommand();
            SelectionChangedCommand.Where(x => x != null)
                .Select(x => ((IEnumerable) x).Cast<TrackStateViewModel>())
                .Subscribe(x => SelectedItems = x);

            RemoveSelectedCommand = new ReactiveCommand();
            RemoveSelectedCommand.Subscribe(param =>
                new List<TrackStateViewModel>(SelectedItems)
                    .ForEach(x => Playlist.Remove(x)));

            RemoveAllCommand = new ReactiveCommand();
            RemoveAllCommand.Subscribe(param => Playlist.Clear());

            PlaySelectedCommand = new ReactiveCommand();
            PlaySelectedCommand.Subscribe(param => _playbackController.Play(SelectedItems.First()));
        }

        public MapManagementVM(
            IConnectivityService Network,
            IMapTransferService MapService,
            IMapStorageService MapStorage,
            INotificationService Notifications,
            [Dispatcher] IScheduler Dispatcher
            ) {
            Contract.Requires(Network != null);
            Contract.Requires(MapService != null);
            Contract.Requires(MapStorage != null);
            Contract.Requires(Notifications != null);
            this.Network = Network;
            this.MapService = MapService;
            this.MapStorage = MapStorage;



            this.FirstActivation()
                .Subscribe(_ => getMaps.Execute(null));

            MapList = getMaps.RegisterAsyncFunction(_ => MapStorage.getAllMaps().Select(m => new MapVM(m)))
                      .SelectMany(vms => vms.ToList())
                      .ObserveOn(Dispatcher)
                      .CreateCollection();
            MapList.ItemsAdded
                .Subscribe(item => _local_map_register.Add(item.ServerKey, Unit.Default));

            MapList.ItemsRemoved
                .Subscribe(item => _local_map_register.Remove(item.ServerKey));

            SelectMap = new ReactiveCommand<MapVM>(vm => !vm.IsDownloading);
            SelectMap
                .Select(vm => vm as IElementVM<Map>)
                .ToMessage(Messenger, MessageContracts.VIEW);

            SelectMap
                .Select(_ => Page.Previous)
                .ToMessage(Messenger);

            DeleteMap = new ReactiveCommand<MapVM>(vm => !vm.IsDownloading);
            DeleteMap
                .Do(vm => MapList.Remove(vm))
                .Select(vm => vm.Model)
                .Where(map => map != null)
                .Subscribe(map => MapStorage.deleteMap(map));

            _IsOnlineAvailable = this.ObservableToProperty(
                this.OnActivation()
                .SelectMany(Network.WifiAvailable().TakeUntil(this.OnDeactivation()))
                .Do(x => { })
                , x => x.IsOnlineAvailable, false);

            SearchMaps = new ReactiveAsyncCommand(_IsOnlineAvailable);

            _SearchResults = this.ObservableToProperty<MapManagementVM, IReactiveCollection<MapVM>>(
                SearchMaps.RegisterAsyncFunction(s => searchMapsImpl(s as string))
                .ObserveOn(Dispatcher)
                .Select(result => {
                    try {
                        return new ReactiveCollection<MapVM>(result.Select(x => new MapVM(null) { ServerKey = x })) as IReactiveCollection<MapVM>;
                    }
                    catch (Exception) {
                        return null;
                    }
                }),
                x => x.SearchResults);

            DownloadMap = new ReactiveCommand<MapVM>(vm => canBeDownloaded(vm as MapVM), Observable.Empty<Unit>());
            DownloadMap
                .Where(downloadMap.CanExecute)
                .CheckConnectivity(Network, Notifications)
                .Do(vm => vm.IsDownloading = true)
                .Do(_ => CurrentPivot = Pivot.Local)
                .Do(vm => MapList.Add(vm))
                .Subscribe(downloadMap.Execute);

            downloadMap.RegisterAsyncObservable(vm => {
                var vm_t = vm as MapVM;
                if (vm_t == null)
                    return Observable.Empty<System.Tuple<MapVM, Map>>();
                else
                    return MapService.downloadMap(vm_t.ServerKey)
                        .ShowServiceErrorNotifications(Notifications)
                        .Catch((WebException ex) => {
                            Notifications.showNotification(DiversityResources.MapManagement_Message_NoPermissions);

                            return Observable.Empty<Map>();
                        })
                        .Select(map => System.Tuple.Create(vm_t, map));
            })
            .ObserveOn(Dispatcher)
            .Select(t => {
                if (t.Item1 != null) // VM
                    {
                    if (t.Item2 != null) // Map
                        {
                        t.Item1.SetModel(t.Item2);
                    }
                    else {
                        MapList.Remove(t.Item1);
//.........这里部分代码省略.........