Question

I’m building a Windows 8 Metro Application where I need to filter an ObservableCollection. Sadly, the CollectionViewSource-Class in the WinRT-Framework doesn’t support filtering so I try to use an IValueConverter for doing so.

My XAML:

<RadioButton Content="this Week" GroupName="AppointmentFilter" IsChecked="True" Name="rbtnFilter"/>
<RadioButton Content="all" GroupName="AppointmentFilter"/>
<ListView ItemsSource="{Binding Appointments, ConverterParameter={Binding rbtnFilter.IsChecked}, Converter={StaticResource Filter}}"/>

My IValueConverter:

public class AppointmentListFilter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        ObservableCollection<VMAppointment> appointments = value as ObservableCollection<VMAppointment>;
        bool filter = (bool)parameter;

        if (filter)
        {
            return new ObservableCollection<VMAppointment>(appointments.Where(x => x.Date.CompareTo(DateTime.Now.AddDays(7)) <= 0));
        }
        else
        {
            return appointments;
        }
    }

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

When the IValueConverter is being executed, the parameter “parameter” is null and not a boolean value. What am I doing wrong?

Answer 1

If binding itself does not support bindings you could change the type of the Appointments property so it includes the parameter you want.
If your converter only gets called once – you could try to subscribe to the ObservableProperty’s CollectionChanged event and raise the PropertyChanged event for Appointments every time it happens.