I have an extremely simple IMultiValueConverter that simply OR's two values. In the example below, I want to invert the first value using an equally simple boolean inverter.
<MultiBinding Converter="{StaticResource multiBoolToVis}">
<Binding Path="ConditionA" Converter="{StaticResource boolInverter}"/>
<Binding Path="ConditionB"/>
</MultiBinding>
and the inverter:
public class BoolInverterConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value is bool)
{
return !((bool)value);
}
return null;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
#endregion
}
When I include the boolInverter, the first value in the MultiValueConverter becomes a "DependencyProperty.UnsetValue". There are no problems when I do not use the converter (other than not the logic I am aiming for, of course).
Am I missing something? Stepping through the debugger shows that the InverseBoolConverter is properly inverting the value I pass it, but that value is then not being 'sent' to the MultiValueConverter.
From MSDN:
UnsetValue is a sentinel value that is used for scenarios where the WPF property system is unable to determine a requested DependencyProperty value. UnsetValue is used rather than null reference (Nothing in Visual Basic), because null reference could be a valid property value, as well as a valid (and frequently used) DefaultValue.
Which means one of the following things:
ControlTemplate
or DataTemplate
), and the value does not have a DataSource set at the time of being Loaded. So it will hit your converter twice, first with the UnsetValue, second with the boolean value; so nothing to worry about;Binding
is incorrect, meaning the Binding cannot determine a value, thus resulting in the UnsetValue.. You should propbably see a warning..Also, you cannot combine Converters like you do.. So its probably that.
Remove the Converter in the inner Binding, and it should be fixed! :)
Hope this helps!