CODEWITHSUNDEEP
c#wpfmvvm
Spoons
Spoons

Reputation: 43

Binding DataContext only if ObservableCollection member is not Null

I have a ObservableCollection of Viewmodels that I want to bind to multiples of the same view but I only want to do the binding if the ObservableCollection member is not null is this possible?

<local:GenericView DataContext="{Binding GenericCollection[0]}"/>
<local:GenericView DataContext="{Binding GenericCollection[1]}"/>
<local:GenericView DataContext="{Binding GenericCollection[2]}"/>

The ObservableCollection is of variable length and not all members will be present.

Upvotes: 1

Views: 276

Answers (1)

mm8
mm8

Reputation: 169270

If GenericCollection[x] is null, there is nothing to bind to. If you want to check whether GenericCollection[x] is null, or don't have an item at all at index x, you could use a converter that returns Binding.DoNothing in case there is no collection.

Something like this:

public class Converter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        IList genericCollection = value as IList;
        int index = System.Convert.ToInt32(parameter);

        if (genericCollection.Count > index)
        {
            object collection = genericCollection[index];
            if (collection != null)
                return collection;
        }

        return Binding.DoNothing;
    }

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

XAML:

<local:GenericView DataContext="{Binding GenericCollection, ConverterParameter=1, Converter={StaticResource converter}}"/>

Upvotes: 2

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