WPF Binding Boolean to an Enum Value

Imagine the situation where you have three radio buttons in a Window. You want the selection of those radio buttons to be bound to a single enum value where the enum contains values for each of the radio button options.

Radio Button: None
Radio Button: Blacklist
Radio Button: Whitelist

public enum FilterType
{
    None,
    Whitelist,
    Blacklist
}

When the bound value changes, the radio button selections should match it. When a radio button selection is changed, the bound value should match the selection.

Problem: How can you do this with only a binding?

Solution: Implement a custom IValueConverter to use on the binding.

public class EnumToBoolConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object trueValue, System.Globalization.CultureInfo culture)
    {
        if (value != null && value.GetType().IsEnum)
            return (Enum.Equals(value, trueValue));
        else
            return DependencyProperty.UnsetValue;
    }

    public object ConvertBack(object value, Type targetType, object trueValue, System.Globalization.CultureInfo culture)
    {
        if (value is bool && (bool)value)
            return trueValue;
        else
            return DependencyProperty.UnsetValue;
    }

    #endregion
}

The idea of this converter is that you bind the converter parameter to the static value of the enum value for which it should return true. Any other value will return false. The reverse conversion works the same way, returning the converter parameter if the binding is true, otherwise returning DependencyProperty.UnsetValue.

<Window.Resources>
    <my:EnumToBoolConverter x:Key="filterTypeConverter" />
</Window.Resources>
...
<RadioButton Name="rdoNone" Content="None" 
             IsChecked="{Binding FilterType, Converter={StaticResource filterTypeConverter}, ConverterParameter={x:Static my:FilterType.None}}" />
<RadioButton Name="rdoBlacklist" Content="Blacklist" 
             IsChecked="{Binding FilterType, Converter={StaticResource filterTypeConverter}, ConverterParameter={x:Static my:FilterType.Blacklist}}" />
<RadioButton Name="rdoWhitelist" Content="Whitelist" 
             IsChecked="{Binding FilterType, Converter={StaticResource filterTypeConverter}, ConverterParameter={x:Static my:FilterType.Whitelist}}" />

I hope this helps you think in a binding oriented way. WPF bindings are very powerful and make your life easier by reducing code and being declarative of the intent.