trjhtr

This is a practice application that I built to learn Rx.Net & RxUI. It follows the MVVM pattern and is written in C# with WPF. Here is a link to a question I asked during the development, which includes some information about this application. Now that it finally runs, I want to improve it by eliminating any potential flaws in the code, which is presented as follows:

public class MainViewModel : ReactiveObject

 #region Constructors

 public MainViewModel()
 
 _currentState = new BehaviorSubject<MainViewModelState>(MainViewModelState.Idle);

 _status = _currentState.Select(s => s.ToString()).ObserveOn(RxApp.MainThreadScheduler)
 .ToProperty(this, nameof(Status));
 _progress = _currentState.Select(s => ((int) s).ToString()).ObserveOn(RxApp.MainThreadScheduler)
 .ToProperty(this, nameof(Progress));

 var canSearch = this.WhenAnyValue(x => x.TargetUrl, x => !string.IsNullOrEmpty(x))
 .CombineLatest(_currentState, (b, state) => b && _currentState.Value == MainViewModelState.Idle);

 _searchCommand = ReactiveCommand.Create(() =>
 
 _currentState.OnNext(MainViewModelState.FetchingHtmlDoc);
 return TargetUrl;
 , canSearch);

 _searchCommand.SelectMany(HtmlDownloadService.GetHtmlDocument)
 .Zip(_searchCommand, Tuple.Create)
 .Do(_ => _currentState.OnNext(MainViewModelState.ExtractingImageUrl))
 .Select(tuple => ImageExtractService.ExtractAllImageAddress(tuple.Item1, tuple.Item2).Distinct())
 .SubscribeOn(RxApp.TaskpoolScheduler)
 .ObserveOn(RxApp.MainThreadScheduler)
 .Subscribe(
 urls =>
 
 _currentState.OnNext(MainViewModelState.PopulatingList);
 urls.ToObservable().ObserveOn(RxApp.MainThreadScheduler).Subscribe(url =>
 ImageList.Add(new ScrappedWebImageViewModel ImageUrl = url));
 _currentState.OnNext(MainViewModelState.Idle);
 ,
 ex => this.Log().Error(ex));

 var canClear = _currentState.Select(x => x == MainViewModelState.Idle).ObserveOn(RxApp.MainThreadScheduler);

 _clearCommand = ReactiveCommand.Create(() =>
 
 _currentState.OnNext(MainViewModelState.ClearingList);
 ImageList.Clear();
 _currentState.OnNext(MainViewModelState.Idle);
 , canClear, RxApp.MainThreadScheduler);
 

 #endregion

 #region Properties

 private IHtmlDownloadService _htmlDownloadService;

 private IHtmlDownloadService HtmlDownloadService =>
 _htmlDownloadService ?? (_htmlDownloadService = Locator.Current.GetService<IHtmlDownloadService>());

 private IImageExtractService _imageExtractService;

 private IImageExtractService ImageExtractService =>
 _imageExtractService ?? (_imageExtractService = Locator.Current.GetService<IImageExtractService>());

 private readonly BehaviorSubject<MainViewModelState> _currentState;

 public ReactiveList<ScrappedWebImageViewModel> ImageList =
 new ReactiveList<ScrappedWebImageViewModel>();

 private readonly ObservableAsPropertyHelper<string> _status;

 public string Status => _status.Value;

 private readonly ObservableAsPropertyHelper<string> _progress;

 public string Progress => _progress.Value;

 private string _targetUrl;

 public string TargetUrl
 
 get => _targetUrl;
 set => this.RaiseAndSetIfChanged(ref _targetUrl, value);
 

 #endregion

 #region Commands

 private readonly ReactiveCommand<Unit, string> _searchCommand;

 public ICommand SearchCommand => _searchCommand;

 private readonly ReactiveCommand<Unit, Unit> _clearCommand;

 public ICommand ClearCommand => _clearCommand;

 #endregion

 #region Methods


 #endregion

 #region Types

 private enum MainViewModelState
 
 Idle = 0,
 FetchingHtmlDoc,
 ExtractingImageUrl,
 PopulatingList,
 ClearingList
 

 #endregion

During my test runs, I noticed that when extracting Urls, the UI became unresponsive, but I can't figure out a better way to do it. Also I wish to add cancellation functionalities but it seems quite difficult to implement with the current code, perhaps I'm not following the best practice?