Winui 3 Combobox in datagrid not displaying data

I am migrating a WPF app to WinUI3. Things went well until I needed to put a combo box in the datagrid. That MS had removed the datagrid from the standard tools was overcome with Community Toolkit Controls.

I can make a column with a combobox, but I have not managed to link it correctly to the data I need to select from. Let's say that it is a page to display books with their primary genre in the combobox.

I use MVVM for connecting the view and data. Showing the main part of the data for the page works. However, the combobox for genres is empty.

The window:

<Grid x:Name="RootGrid">
    <ctWUI3:DataGrid x:Name="tasksDataGrid"
                     AutoGenerateColumns="False" 
                     GridLinesVisibility="All"
                     CanUserSortColumns="True"
                     ScrollViewer.VerticalScrollBarVisibility="Auto"
                     AlternatingRowBackground="LightGray"
                     ItemsSource="{Binding Books}" 
                     Margin="10,0,5,0" 
                     RowDetailsVisibilityMode="VisibleWhenSelected">
        <ctWUI3:DataGrid.Columns>
            <ctWUI3:DataGridTextColumn Binding="{Binding Id}"
                        		Header="Name" 
								Width="150"
                        		IsReadOnly="False" />
            <ctWUI3:DataGridTextColumn Binding="{Binding Title}"
                        		Header="Name" 
								Width="150"
                        		IsReadOnly="False" />
            <ctWUI3:DataGridTextColumn Binding="{Binding Description}"
                        		Header="Description" 
								Width="150"
                        		IsReadOnly="False" />
            <ctWUI3:DataGridTextColumn Binding="{Binding PrimaryGenreId}"
                        		Header="Genre" 
								Width="150"
                        		IsReadOnly="False" />
            <ctWUI3:DataGridComboBoxColumn Binding="{Binding PrimaryGenreId}"
                                           Header="Genre" 
                                           ItemsSource="{Binding Genres, Mode=OneWay}"
                                           DisplayMemberPath="Name"
                                           Width="SizeToHeader" />
        </ctWUI3:DataGrid.Columns>
    </ctWUI3:DataGrid>
</Grid>

The xaml.cs

public sealed partial class MainWindow : Window
{
    public MainWindow()
    {
        this.InitializeComponent();
        RootGrid.DataContext = new MainViewModel();
    }
}

Then the MainViewModel.cs contains two private fields, a constructor of test data, and the public getter/setters for the fields.

public ObservableCollection<Book> Books
{
    get => _books;
    set { SetProperty(ref _books, value); }
}

public ObservableCollection<Genre> Genres
{
    get => _genres;
    set { SetProperty(ref _genres, value); }
}

How do I get the combobox to display the genre of the book for that row (using a GenreId field as the foreign key)?

posted 12 months ago

CC BY-SA 4.0

FrankLuke‭

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