WPF binding declarative syntax: enable a GroupBox when a checkbox is NOT set

Question

I'm a WPF newbie, so pardon me in advance if this is a dumb question. I've got syntax for enabling a GroupBox if a checkbox is checked, which works fine:

IsEnabled="{Binding ElementName=cbIsDeceased, Path=IsChecked}"

But what I need is to flip the polarity. I need IsEnabled to be true when the checkbox is NOT checked and vice versa. Is there a declarative way to get that?

Thanks.

Answer 1

You have to add a converter to invert the boolean value. In XAML, define the resource for the converter and add it to the binding:

IsEnabled="{Binding ElementName=cbIsDeceased, Path=IsChecked, Converter={StaticResource InverseBooleanConverter}"

And to spare you some time, I give you my version of the converter, which is extremely simple :)

/// <summary>
/// Converts a boolean to its opposite value
/// </summary>
[ValueConversion(typeof(bool), typeof(bool))]
public class InverseBooleanConverter: IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        if (targetType != typeof(bool))
            throw new InvalidOperationException("The target must be a boolean");

        return !(bool)value;
    }

    public object ConvertBack(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        throw new NotSupportedException();
    }

    #endregion
}