How to bind inverse boolean properties in WPF?

Question

I am open to suggestions with the title. It really is pretty bad.

What I have is an object that has an "IsReadOnly" property. If this property is true, I would like to set the "IsEnabled" property on a Button, ( for example ), to false.

I would like to believe that I can do it as easily as IsEnabled="{Binding Path=!IsReadOnly}" but that doesn't fly with WPF.

Am I relegated to having to go through all of the style settings? Just seems too wordy for something as simple as setting one bool to the inverse of another bool.

 <Button.Style>
                    <Style TargetType="{x:Type Button}">
                        <Style.Triggers>
                            <DataTrigger Binding="{Binding Path=IsReadOnly}" Value="True">
                                <Setter Property="IsEnabled" Value="False" />
                            </DataTrigger>
                            <DataTrigger Binding="{Binding Path=IsReadOnly}" Value="False">
                                <Setter Property="IsEnabled" Value="True" />
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </Button.Style>

Answer 1

You can use a ValueConverter that inverts a bool property for you.

XAML:

IsEnabled="{Binding Path=IsReadOnly, Converter={StaticResource InverseBooleanConverter}}"

Converter:

[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
    }

Answer 2

Have you considered a IsNotReadOnly property? If the object being bound is a ViewModel in a MVVM domain then the additional property makes perfect sense. If it's a direct Entity model, you might consider composition and presenting a specialized viewmodel of your entity to the form.

Answer 3

I opened suggestion to implement Boolean inversion converter to WPF framework (to Microsoft Connect bug/suggestion system)

If you care about this enhancement please vote on it there.

There are many other such weaknesses in WPF that should be addressed also, so if you find such a rudimentary insufficiency I think you should also add it to there. Currently people seem to implement a lot of these "common" / "utility" libraries to accommodate simple tasks that should be part of framework.