How to know the index of the current element of ItemsRepeater in Avalonia?

Question

I have the following code in my MainWindow.axaml :

<ItemsRepeater Items="{Binding ChannelCollection}">
    <ItemsRepeater.ItemTemplate>
        <DataTemplate>
            <CheckBox IsChecked="{Binding Value, Mode=TwoWay}" Content="{Binding Name}"></CheckBox>
        </DataTemplate>
    </ItemsRepeater.ItemTemplate>
</ItemsRepeater>

Here I bind to collection of Channels with Name and Value properties. But actual content of my checkbox depends on its index in the collection. I don't want to resolve the Channel myself but want to use converter that maps index to the name. So far I have to know the element index from the axaml code.

I want to have something like this in my Checkbox tag:

Content="{Binding ItemsRepeater.CurrentIndex, Converter={StaticResource IdToNameConverter}}"

How can I do this?

ItemsRepeater doesn't have a SelectedIndex property. You should try with a GridView o ListView. — McNets, Dec 07 '22 at 23:29
It is worth noting that the ItemsRepeater.Index attached property is only available in the context of an ItemsRepeater control, so it cannot be used outside of an ItemsRepeater item template. If you need to access the index of an item outside of an ItemsRepeater context, you could use a different approach, such as storing the index of the item in the item's data object and binding to that property instead. — jazb, Dec 08 '22 at 03:52

score 1 · Accepted Answer · answered Dec 08 '22 at 09:07

You could use a multi value converter that converts your collection and the element to the name string:

public class ElementIndexConverter : IMultiValueConverter
{
    public object Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
    {
        return values[0] is IList list ? $"{list.IndexOf(values[1])}" : "-1";
    }
}

Then in the view you have to use MultiBinding and pass the collection and the object:

<ItemsRepeater Items="{Binding ChannelCollection}">
    <ItemsRepeater.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <CheckBox IsChecked="{Binding Value, Mode=TwoWay}">
                    <CheckBox.Content>
                        <MultiBinding Converter="{StaticResource ElementIndexConverter}">
                            <MultiBinding.Bindings>
                                <Binding Path="$parent[ItemsRepeater].DataContext.ChannelCollection"/>
                                <Binding Path="."/>
                            </MultiBinding.Bindings>
                        </MultiBinding>
                    </CheckBox.Content>
                </CheckBox>
            </StackPanel>
        </DataTemplate>
    </ItemsRepeater.ItemTemplate>
</ItemsRepeater>

How to know the index of the current element of ItemsRepeater in Avalonia?

1 Answers1