WPF MVVM Radio buttons on ItemsControl

Question

I've bound enums to radio buttons before, and I generally understand how it works. I used the alternate implementation from this question: How to bind RadioButtons to an enum?

Instead of enumerations, I'd like to generate a runtime-enumerated set of a custom type and present those as a set of radio buttons. I have gotten a view working against a runtime-enumerated set with a ListView, binding to the ItemsSource and SelectedItem properties, so my ViewModel is hooked up correctly. Now I am trying to switch from a ListView to a ItemsControl with radio buttons.

Here's as far as I've gotten:

<Window.Resources>
    <vm:InstanceToBooleanConverter x:Key="InstanceToBooleanConverter" />
</Window.Resources>

<!-- ... -->

<ItemsControl ItemsSource="{Binding ItemSelections}">
    <ItemsControl.ItemTemplate>
        <DataTemplate DataType="{x:Type vm:ISomeType}">
            <RadioButton Content="{Binding Name}"
                         IsChecked="{Binding Path=SelectedItem, Converter={StaticResource InstanceToBooleanConverter}, ConverterParameter={Binding}}"
                         Grid.Column="0" />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

InstanceToBooleanConverter has the same implementation as EnumToBooleanConverter from that other question. This seems right, since it seems like it just invokes the Equals method:

public class InstanceToBooleanConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return value.Equals(parameter);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return value.Equals(true) ? parameter : Binding.DoNothing;
    }
}

The problem I am getting now is that I can't figure out how to send a runtime value as the ConverterParameter. When I try (with the code above), I get this error:

A 'Binding' cannot be set on the 'ConverterParameter' property of type 'Binding'. A 'Binding' can only be set on a DependencyProperty of a DependencyObject.

Is there a way to bind to the item instance, and pass it to the IValueConverter?

Answer 1

It turns out that it is much simpler to abandon using ItemsControl and instead go with ListBox.

It may be more heavy-weight, but that's mostly because it is doing the heavy lifting for you. It is really easy to do a two-way binding between RadioButton.IsChecked and ListBoxItem.IsSelected. With the proper control template for the ListBoxItem, you can easily get rid of all the selection visual.

<ListBox ItemsSource="{Binding Properties}" SelectedItem="{Binding SelectedItem}">
    <ListBox.ItemContainerStyle>
        <!-- Style to get rid of the selection visual -->
        <Style TargetType="{x:Type ListBoxItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBoxItem}">
                        <ContentPresenter />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </ListBox.ItemContainerStyle>
    <ListBox.ItemTemplate>
        <DataTemplate DataType="{x:Type local:SomeClass}">
            <RadioButton Content="{Binding Name}" GroupName="Properties">
                <!-- Binding IsChecked to IsSelected requires no support code -->
                <RadioButton.IsChecked>
                    <Binding Path="IsSelected"
                             RelativeSource="{RelativeSource AncestorType=ListBoxItem}"
                             Mode="TwoWay" />
                </RadioButton.IsChecked>
            </RadioButton>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>