c# - Bind RadioButtons to single property?

Question

• I'm having few RadioButtons and I don't want to bind "IsChecked" property of each one of them to unique property in the code.
• I want to have a single property like "CurrentSelected" and according to that to set the "IsChecked".
• In addition I don't want to use converters.

• I tried to use the behavior "ChangePropertyAction" but it looks like it's working only in one way. here is my code:

  <RadioButton
      x:Name="UpRadioButton"
      Margin="5"
      Content="Up"
      >
      <i:Interaction.Triggers>
          <ei:DataTrigger Binding="{Binding IsChecked, ElementName=UpRadioButton}" Value="True">
              <ei:ChangePropertyAction TargetObject="{Binding Mode=OneWay}" PropertyName="SelectedDirection" Value="{x:Static Enums:DirectionEnum.Up}" />
          </ei:DataTrigger>
      </i:Interaction.Triggers>
  </RadioButton>
  
  <RadioButton
      x:Name="DownRadioButton"
      Margin="5"
      Content="Down"
      >
      <i:Interaction.Triggers>
          <ei:DataTrigger Binding="{Binding IsChecked, ElementName=DownRadioButton}" Value="True">
              <ei:ChangePropertyAction TargetObject="{Binding Mode=OneWay}" PropertyName="SelectedDirection" Value="{x:Static Enums:DirectionEnum.Down}" />
          </ei:DataTrigger>
      </i:Interaction.Triggers>
  </RadioButton>
  
  <RadioButton
      x:Name="LeftRadioButton"
      Margin="5"
      Content="Left"
      >
      <i:Interaction.Triggers>
          <ei:DataTrigger Binding="{Binding IsChecked, ElementName=LeftRadioButton}" Value="True">
              <ei:ChangePropertyAction TargetObject="{Binding Mode=OneWay}" PropertyName="SelectedDirection" Value="{x:Static Enums:DirectionEnum.Left}" />
          </ei:DataTrigger>
      </i:Interaction.Triggers>
  </RadioButton>
  
  <RadioButton
      x:Name="RightRadioButton"
      Margin="5"
      Content="Right"
      >
      <i:Interaction.Triggers>
          <ei:DataTrigger Binding="{Binding IsChecked, ElementName=RightRadioButton}" Value="True">
              <ei:ChangePropertyAction TargetObject="{Binding Mode=OneWay}" PropertyName="SelectedDirection" Value="{x:Static Enums:DirectionEnum.Right}" />
          </ei:DataTrigger>
      </i:Interaction.Triggers>
  </RadioButton>               
  

my view model is very simple: MainViewModel.cs

public class MainViewModel : ViewModelBase
{ 
    private DirectionEnum _selectedDirection;

    public DirectionEnum SelectedDirection
    {
        get { return _selectedDirection; }
        set
        {
            if (_selectedDirection != value)
            {
                _selectedDirection = value;
                RaisePropertyChanged();
            }
        }
    }
    public MainViewModel()
    {     
        SelectedDirection = DirectionEnum.Up;            
    }  
}

as you can see from the code, the "Up" RadioButton should be already checked... What am I missing ?

Answer 1

A common solution for me is to use a ListBox, which contains Selection behavior, and overwrite the Template to draw items as RadioButtons instead.

My XAML template usually looks something like this :

<Style x:Key="RadioButtonListBoxStyle" TargetType="{x:Type ListBox}">
    <Setter Property="BorderBrush" Value="Transparent"/>
    <Setter Property="KeyboardNavigation.DirectionalNavigation" Value="Cycle" />
    <Setter Property="ItemContainerStyle">
        <Setter.Value>
            <Style TargetType="{x:Type ListBoxItem}" >
                <Setter Property="Margin" Value="2, 2, 2, 0" />
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate>
                            <Border Background="Transparent">
                                <RadioButton
                                    Content="{TemplateBinding ContentPresenter.Content}" VerticalAlignment="Center"
                                    IsChecked="{Binding Path=IsSelected,RelativeSource={RelativeSource TemplatedParent},Mode=TwoWay}"/>

                            </Border>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </Setter.Value>
    </Setter>
</Style>

The style is applied like this:

<ListBox ItemsSource="{Binding Directions}"
         SelectedValue="{Binding SelectedDirection}"
         Style="{StaticResource RadioButtonListBoxStyle}" />

I find this much cleaner for managing selection behavior of grouped RadioButtons than maintaining a lot of IsChecked properties in my code-behind, or using converters.