Let's say I have some collection of data. My goal is to provide different kind of view of ItemsControl depending on user`s preference.

For simplicity, we can assume that user can select only between two states - horizontal & vertical.

MCVE

public enum ViewType { H, V }

public class MainWindowViewModel : ViewModelBase
{
    private ViewType _viewType;

    public MainWindowViewModel()
    {
        Values = Enumerable.Range(0, 20).Select(v => v.ToString());
        ViewTypes = new[] { ViewType.H, ViewType.V };
        ViewType = ViewTypes[0];
    }

    public ViewType ViewType
    {
        get => _viewType;
        set => this.RaiseAndSetIfChanged(ref _viewType, value);
    }
    public IEnumerable<string> Values { get; }
    public ViewType[] ViewTypes { get; }
}

  <Grid RowDefinitions="*,Auto">
    <ItemsControl Items="{Binding Values}"
                  Grid.Row="0" />
    <ComboBox Items="{Binding ViewTypes}"
              Grid.Row="1"
              SelectedItem="{Binding ViewType}"/>
  </Grid>

But I wasn't able to find a way to define selector for ItemsPanelTemplate.

When I tried to use converter:

ItemsPanel="{Binding ViewType, Converter={StaticResource ResourceKey=converter}}"

public class ViewTypePanelConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var template = new ItemsPanelTemplate()
        {
            Content = new Func<IServiceProvider, ControlTemplateResult>( _ => {
                var content =
                    value switch
                    {
                        ViewType.V => new StackPanel { Orientation = Orientation.Vertical },
                        ViewType.H => new StackPanel { Orientation = Orientation.Horizontal },
                        _ => throw new NotImplementedException(),
                    };
                return new ControlTemplateResult(content, new NameScope());
            })
        };
        return template;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

it has zero effect.

This Q is inspired by Use DataTemplate for ItemsControl.ItemsPanel #7268 discussion from Avalonia project repo.

posted almost 3 years ago

CC BY-SA 4.0

3y ago

FoggyFinder‭

318 reputation 2 12 33 7