WPF IValueConverter with Radio Buttons

Question

I have a datagrid to which a list of objects is binded. Each object has a Number property. I have 2 radio buttons,if the first is checked then the default value should appear in the column,but if the second radio button is checked, I want to divide the whole column by 1000. I tried using IValueConverter, but when i add the Converter to the Binding of the DataGridTextColumn, the Number column is empty. I DON'T want to change the property in the object, only in the UI. How could I achieve this to work?

The code I tried:

 public class NumberConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is long numValue)
            return numValue / 1000.0;
        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is long numValue)
            return numValue * 1000.0;
        return value;
    }
}

The XAML code:

<Window.Resources>
  <local:NumberConverter x:Key="NumberConverter"/>
</Window.Resources>

               <RadioButton 
                    Grid.Column="1"
                    HorizontalAlignment="Right"
                    x:Name="MultiplyBy1000" 
                    GroupName="chkFormat" 
                    Content="Default" 
                    IsChecked="{Binding IsDefaultChecked}"
                    Margin="5"/>

                <RadioButton 
                    Grid.Column="2"
                    HorizontalAlignment="Left"
                    x:Name="DivideBy1000"
                    GroupName="chkFormat" 
                    Content="Divide by 1000"
                    IsChecked="{Binding IsDivideNumChecked}"
                    Margin="5"/>

....

<DataGridTextColumn Header="Number" Width="0.7*" Binding="{Binding Number,Converter={StaticResource NumberConverter}"/>

Answer 1

You need to use MultiValueConverter and bind the value and the radio button's IsChecked value.

A value converter like the below:

public class ConditionalDividerConverter: IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var divide = (bool)values[0];
        var value = (double)values[1];
        return divide ? value / 1000 : value;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotSupportedException("Not implemented");
    }
}

And the usage of the binding :

<DataGridTextColumn Header="Number" Width="0.7*" >
  <DataGridTextColumn.Binding>
    <MutliBinding Converter="{StaticResource conditionalDividerConverter}">
      <MultiBinding.Bindings>
        <Binding ElementName="DivideBy1000" Path="IsChecked" />
        <Binding Path="Number" />
      </MultiBinding.Bindings>
    </MultiBinding>
  </DataGridTextColumn.Binding>
</DataGridTextColumn>