WPF MVVM Binding to SelectedItem of ListBox within DataTemplate of Parent ListBox

Question

I have a ListBox within a DataTemplate of another ListBox simplified to the following XAML

<ListBox ItemsSource="{Binding MovieList}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <ListBox ItemsSource="{Binding Cast}" 
                         DisplayMemberPath="Name"
                         SelectedItem="{Binding SelectedCastMember, Mode=TwoWay}"/>
                <TextBlock Text="{Binding MovieName}"/>
                <TextBlock Text=....../>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

The Parent List is bound to an ObservableCollection of Movie with each Movie object in turn having an ObservableCollection of cast members bound to a list box. The ViewModel property and Class below

public const string MovieListPropertyName = "MovieList";

    private ObservableCollection<Movie> _movieList;

    public ObservableCollection<Movie> MovieList
    {
        get
        {
            return _movieList;
        }

        set
        {
            if (_movieList == value)
            {
                return;
            }

            RaisePropertyChanging(MovieListPropertyName);
            _movieList = value;
            RaisePropertyChanged(MovieListPropertyName);
        }
    }

public const string SelectedCastMemberPropertyName = "SelectedCastMember";

    private MovieCastMember _selectedCastMember;

    public MovieCastMember SelectedCastMember
    {
        get
        {
            return _selectedCastMember;
        }

        set
        {
            if (_selectedCastMember == value)
            {
                return;
            }

            RaisePropertyChanging(SelectedCastMemberPropertyName);
            _selectedCastMember = value;
            RaisePropertyChanged(SelectedCastMemberPropertyName);
        }
    }

With the Movie and MovieCastMember classes as follows

    public class Movie
    {                    
        public int Id { get; set; }
        public string Name { get; set; }
        public int Year { get; set; }
        public string Overview { get; set; }
        public double VoteAverage { get; set; }
        public ObservableCollection<MovieCastMember> Cast { get; set; }
        public BitmapImage PosterImage { get; set; }       
    }

    public class MovieCastMember
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

I want to select a cast member in any of the Movie Lists and bind the MovieCastMember object to a property in my ViewModel. My List boxes populates fine, I have tried various scenarios in XAML but the SelectedItem are not updating the property in the ViewModel. Any help would be appreciated.

Erti-Chris Eelmaa Erti-Chris Eelmaa · Accepted Answer · 2013-12-22T22:10:54

That's because you're binding against Movie class in second listBox. There is no "SelectedCastMember". Move it to Movie class and it will work.

WPF MVVM Binding to SelectedItem of ListBox within DataTemplate of Parent ListBox

1 Answers