Question

I need to set a TextBlock’s Text to something like “Name (number of items with not null property)”. Right now, I’m doing this using the number of items of the entire collection, using ItemsSource.Count.

<TextBlock x:Name="textBlockHeader" >
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource headerCreator}" x:Name="multiBinder">
            <Binding ElementName="trackingTable" Path="Name" />
            <Binding ElementName="trackingsGrid" Path="ItemsSource.Count" />
        </MultiBinding>
    </TextBlock.Text>
</TextBlock> 

For that I’m using an IMultiValueConverter:

internal class HeaderCreator : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        // Based on this xaml
        ////<Binding ElementName="trackingTable" Path="Name" />                 values[0]
        ////<Binding ElementName="trackingsGrid" Path="ItemsSource.Count" />    values[1]

        return values[0] + " (" + values[1] + ")";
    }

trackingsGrid is a DataGrid defined below (not showing code here), binded to the collection, which has TrackingData objects. TrackingData has a property called Tracking. I need to count only the items in the ObservableCollection that has this property as not null. How can I achieve this?

public class TrackingData : INotifyPropertyChanged
{
    public Model.ITracking Tracking { get; set; }
    ...
}

Thanks in advance.

Answer 1

Put this logic (… items in the ObservableCollection that has this property as not null) in your ViewModel and bind to this property.