CODEWITHSUNDEEP
c#wpfopacityivalueconverter
demo
demo

Reputation: 6235

InvalidOperationException: The target must be a boolean

I have UserControl. In it I have Grid. To this Grid I set Opacity which is 0 or 1 according to value of another control. To set it I am using next converter :

[ValueConversion(typeof(bool), typeof(double))]
public class OpacityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var b = value as bool?;
        if (targetType != typeof(bool) && !b.HasValue)
            throw new InvalidOperationException("The target must be a boolean");
        if (b.HasValue)
        {
            return b.Value ? 1 : 0;
        }
        return 0;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Converter which transform bool value into Opacity. For me it all seems correct.

But when I go to designer of page where I use that UserControl I see error

InvalidOperationException: The target must be a boolean at SizeStream.WPF.Converters.OpacityConverter.Convert(Object value, Type targetType, Object parameter, CultureInfo culture)

When I build my project everything is Ok. But In designer - not.

Restarting VS 2013 doesn't help.

Why there are such problem? Thanks

<controls:MultiSelectComboBox Tag="{Binding PanelLoading, Converter={StaticResource InverseConverter}}" SelectedItems="{Binding SelectedBrandsList, Mode=TwoWay}"  Grid.Column="2" Grid.Row="0" x:Name="BrandsFilter" DefaultText="Brand" ItemsSource="{Binding BrandsList}" Style="{StaticResource FiltersDropDowns}"/>

From this element I get Tag value.

<Grid Background="#FF826C83" Name="DropDown" SnapsToDevicePixels="True" MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding MaxDropDownHeight}" Opacity="{Binding Path=Tag, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}, Converter={StaticResource OpacityConverter}}">

Here I use converter

Answer :

With help of StackOverflow users my final code looks like :

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (targetType != typeof(double))
            throw new InvalidOperationException("The target must be a double");
        if (value is bool)
        {
            return (bool)value ? 1 : 0;
        }
        return 0;
    }

Upvotes: 0

Views: 1170

Answers (1)

bkdev
bkdev

Reputation: 432

if (targetType != typeof(bool) && !b.HasValue)
        throw new InvalidOperationException("The target must be a boolean");

If you intend to convert from bool to double, then your target type must be checked against "double" in the above code.

Upvotes: 1

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