RaisePropertyChanged 不更新 UI

Question

当我的 ViewModel 更改时，我无法让 UI 更新两个列表框以正确更新。

首先，页面背后的基本逻辑：

Movie是一个带有标题的对象，以及各种MovieDetails。有些 MovieDetail 与其他的不同，因为它们详细，这是一种美化的方式来表达它们更重要。 我使用两个 ListBoxes 将这些 MovieDetails 分成堆叠 ListBoxes，一个用于“Detailed”，一个用于“NotDetailed” ' 如果电影没有“详细”属性，则相应的列表将通过 BooleanToVisibilityConverter 隐藏（反之亦然）

当我导航到该页面时，我将 Movie 设置为页面对应，并且应该 RaisePropertyChanged 来提醒 AllMoviesDetail ObservableCollection 它应该重新获取Movies.MovieDetailFetchedList。 从那里，AllMoviesDetail 将提醒两个 ObservableCollections（Detailed、NotDetailed） 它们应该重新获取。

事实上，NotDetailedMovieDetails 或 DetailedMovieDetails 上的 RaisePropertyChanged 似乎也没有执行任何操作。 （以及相应的 HasNotDetailedMovieDetails, Has...）

但是，有效的是，如果我向列表中添加更多项目，CollectionChanged 事件似乎会触发并重新激活列表。我还可以通过在代码中首先实例化 ObservableCollections 来实现此目的 var temp =DetailedMoviesDetail;

public class MoviesDetailViewModel : ViewModelBase
{
    #region Property Names

    public const string MoviePropertyString = "Movie";
    public const string AllMoviesDetailPropertyString = "AllMoviesDetail";
    public const string DetailedMoviesDetailPropertyString = "DetailedMoviesDetail";
    public const string NotDetailedMoviesDetailPropertyString = "NotDetailedMoviesDetail";
    public const string HasNotDetailedMoviesDetailPropertyString = "HasNotDetailedMoviesDetail";
    public const string HasDetailedMoviesDetailPropertyString = "HasDetailedMoviesDetail";
    public const string NotDetailedHeaderPropertyString = "NotDetailedHeader";

    #endregion


    public MoviesDetailViewModel()
    {
        if (IsInDesignMode)
        {
            Movie = DesignDataStore.MovieList[0];
            Movie.Category = Category.DDA;
        }
    }

    private Movie _Movie;

    /// <summary>
    /// The Movie for which to browse MoviesDetail. It is expected when setting this property, that MoviesDetail for it have been downloaded previously.
    /// </summary>
    /// <remarks>The 'Master' property for this ViewModel. All properties are Dependent on this and the underlying property MoviesDetailList</remarks>
    /// <seealso cref="MovieDetailFetchedList"/>
    public Movie Movie
    {
        get { return _Movie; }
        set
        {
            if (_Movie != value)
            {
                if (_Movie != null)
                    _Movie.MovieDetailFetchedList.CollectionChanged -= MoviesDetailListChanged;


                _Movie = value;

                RaisePropertyChanged(MoviePropertyString);
                RaisePropertyChanged(StatementPeriodAvailablePropertyString);
                RaisePropertyChanged(NotDetailedMoviesDetailPropertyString);
                Movie.MovieDetailFetchedList.CollectionChanged += MoviesDetailListChanged;

                RaisePropertyChanged(AllMoviesDetailPropertyString);

                RaisePropertyChanged(DetailedMoviesDetailPropertyString);

                RaisePropertyChanged(NotDetailedHeaderPropertyString);
            }
        }
    }

    private void MoviesDetailListChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Add)
        {
            foreach (var item in e.NewItems)
            {
                if (((MovieDetail) item).IsDetailed())
                    DetailedMoviesDetail.Add(item as MovieDetail);
                else
                    NotDetailedMoviesDetail.Add(item as MovieDetail);
            }
        }
        else
        {
            RaisePropertyChanged(AllMoviesDetailPropertyString);
            RaisePropertyChanged(DetailedMoviesDetailPropertyString);
            RaisePropertyChanged(NotDetailedMoviesDetailPropertyString);
        }
    }




    #endregion

    private MovieDetailFetchedList _allMoviesDetail;
    public MovieDetailFetchedList AllMoviesDetail
    {
        get
        {
            if (Movie == null)
                return new MovieDetailFetchedList();

            return _allMoviesDetail ?? (AllMoviesDetail = Movie.MovieDetailFetchedList);
        }
        set
        {
            if (_allMoviesDetail != value)
            {
                if (_allMoviesDetail != null)
                    _allMoviesDetail.CollectionChanged -= MoviesDetailListChanged;
                _allMoviesDetail = value;
                _allMoviesDetail.CollectionChanged += MoviesDetailListChanged;

                RaisePropertyChanged(AllMoviesDetailPropertyString);
                //force update
                DetailedMoviesDetail = NotDetailedMoviesDetail = null;
                RaisePropertyChanged(DetailedMoviesDetailPropertyString);
                RaisePropertyChanged(HasDetailedMoviesDetailPropertyString);
                RaisePropertyChanged(NotDetailedMoviesDetailPropertyString);
                RaisePropertyChanged(HasNotDetailedMoviesDetailPropertyString);
            }

        }
    }

    public bool HasNotDetailedMoviesDetail { get { return NotDetailedMoviesDetail != null && NotDetailedMoviesDetail.Count > 0; } }



    private ObservableCollection<MovieDetail> _notDetailedMoviesDetail;
    public ObservableCollection<MovieDetail> NotDetailedMoviesDetail
    {
        get
        {
            if (Movie == null) return new ObservableCollection<MovieDetail>();

            return AllMoviesDetail;
               return _notDetailedMoviesDetail ?? //make sure RaisePropertyChanged happens by using property setter
              (NotDetailedMoviesDetail = AllMoviesDetail.Where(mem => !mem.IsDetailed()).ToObservableCollection());
        }
        set
        {
            _notDetailedMoviesDetail = value;
            RaisePropertyChanged(NotDetailedMoviesDetailPropertyString);
            RaisePropertyChanged(HasNotDetailedMoviesDetailPropertyString);
        }
    }

    public bool HasDetailedMoviesDetail
    { get { return DetailedMoviesDetail != null && DetailedMoviesDetail.Count > 0; } }

    private ObservableCollection<MovieDetail> _DetailedMoviesDetail;
    public ObservableCollection<MovieDetail> DetailedMoviesDetail
    {
        get
        {
            if (Movie == null) return new ObservableCollection<MovieDetail>();

            return AllMoviesDetail;
            return _DetailedMoviesDetail ?? //make sure RaisePropertyChanged happens by using property setter
            (DetailedMoviesDetail = AllMoviesDetail.Where(mem => mem.IsDetailed()).ToObservableCollection());
        }
        set
        {
            _DetailedMoviesDetail = value;
            RaisePropertyChanged(DetailedMoviesDetailPropertyString);
            RaisePropertyChanged(HasDetailedMoviesDetailPropertyString);
        }
    }


    private string _DetailedHeader;
    public string DetailedHeader
    {
        get { return _DetailedHeader ?? (_DetailedHeader = AppResources.in_available); }
        set { _DetailedHeader = value; }
    }

    public string NotDetailedHeader
    {
        get { return (Movie != null && Movie.Category == Category.DRAMA) ? AppResources.Movie_MoviesDetail : AppResources.not_in_available; }
    }
}

Answer 1

所有属性 getter（AllMoviesDetail 除外）都有两个 return 语句。由于仅执行第一个，因此不会分配值，并且不会触发 PropertyChanged 事件。