Question

I have a list of data where I keep e.g. countries with code, name and some other data.

List<Country> countries = <deserialized objects from file>

which consist of objects like this:

  public class Country
  {
       public string Code { get; set;}
       public string Name { get; set;}
  }

The object which use as a DataContext may look like this:

public class Address
{
    public string StreetName{ get; set;}
    public string CountryCode { get; set;}
}

Then in my XAML I want to do something like this to show the name of the country

<TextBlock Text="{Binding Path=CountryCode, Converter={StaticResource CountryNameLookupConverter}}"/>

But how can I make the CountryNameLookupConverter use the countries list I read from the xml file?

Answer 1

Depending on where you’re exposing the countries collection there are a few different options.

If countries exists in Address or some other ViewModel object you change your converter to implement IMultiValueConverter instead of IValueConverter and then use a MultiBinding to pass both CountryCode and countries (exposed as a property). You would then access and cast values[0] and values[1] to use them to do the lookup in the Convert method.

<TextBlock>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource CountryNameLookupConverter}">
            <Binding Path="CountryCode" />
            <Binding Path="Countries" />
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

If you are exposing countries statically (i.e. Lookup.Countries), you can pass the collection to your IValueConverter either as a property or through the ConverterParameter. Here’s the converter with a property:

public class CountryNameLookupConverter : IValueConverter
{
    public IEnumerable<Country> LookupList { get; set; }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        Country country = LookupList.FirstOrDefault(c => c.Code.Equals(value));
        if (country == null)
            return "Not Found";
        return country.Name;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return Binding.DoNothing;
    }
}

and the converter resource would be declared like:

<local:CountryNameLookupConverter x:Key="CountryNameLookupConverter" LookupList="{x:Static local:Lookup.Countries}"/>

Or to pass into Convert’s object parameter instead:

<TextBlock Text="{Binding Path=CountryCode, Converter={StaticResource CountryNameLookupConverter}, ConverterParameter={x:Static local:Lookup.Countries}}" />