WPF element databinding for IsEnabled (but for false)

Question

I'm a starter in WPF, and there's something I can't seem to figure out.

I have a checkbox that I would like to disable when a radio button is not selected. my current syntax is:

<CheckBox IsEnabled="{Binding ElementName=rbBoth, Path=IsChecked}">Show all</CheckBox>

So basically, I want IsEnabled to take the opposite value than the binding expression I'm currently supplying.

How can I do this? Thanks

Answer 1

You need to use what's called a value converter (a class that implements IValueConverter.) A very basic example of such a class is shown below. (Watch for clipping...)

public class NegateConverter : IValueConverter
{

    public object Convert( object value, Type targetType, object parameter, CultureInfo culture )
    {
        if ( value is bool ) {
            return !(bool)value;
        }
        return value;
    }

    public object ConvertBack( object value, Type targetType, object parameter, CultureInfo culture )
    {
        if ( value is bool ) {
            return !(bool)value;
        }
        return value;
    }

}

Then to include it in your XAML you would do something like:

<UserControl xmlns:local="clr-namespace:MyNamespace">
    <UserControl.Resources>
        <local:NegateConverter x:Key="negate" />
    </UserControl.Resources>

    ...
    <CheckBox IsEnabled="{Binding IsChecked, ElementName=rbBoth, Converter={StaticResource negate}}"
              Content="Show all" />

</UserControl>

Answer 2

Your current syntax already serves your need. It will disable the checkbox if the radiobutton is not checked.

If you really want to invert the scenario, all you need is a Converter. Take a look at this sample.