SelectedItemEventArgsConverter

The SelectedItemEventArgsConverter is a converter that allows users to extract the SelectedItem value from an SelectedItemChangedEventArgs object. It can subsequently be used in combination with EventToCommandBehavior.

BaseConverter Properties

The following properties are implemented in the base class, public abstract class BaseConverter:

Property	Description
DefaultConvertReturnValue	Default value to return when IValueConverter.Convert(object?, Type, object?, CultureInfo?) throws an Exception. This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true.
DefaultConvertBackReturnValue	Default value to return when IValueConverter.ConvertBack(object?, Type, object?, CultureInfo?) throws an Exception. This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true.

ICommunityToolkitValueConverter Properties

The following properties are implemented in the public interface ICommunityToolkitValueConverter:

Property	Type	Description
DefaultConvertReturnValue	object?	Default value to return when IValueConverter.Convert(object?, Type, object?, CultureInfo?) throws an Exception. This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true.
DefaultConvertBackReturnValue	object?	Default value to return when IValueConverter.ConvertBack(object?, Type, object?, CultureInfo?) throws an Exception. This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true.

Syntax

XAML

Including the XAML namespace

In order to use the toolkit in XAML the following xmlns needs to be added into your page or view:

xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"

Therefore the following:

<ContentPage
    x:Class="CommunityToolkit.Maui.Sample.Pages.MyPage"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">

</ContentPage>

Would be modified to include the xmlns as follows:

<ContentPage
    x:Class="CommunityToolkit.Maui.Sample.Pages.MyPage"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit">

</ContentPage>

Using the SelectedItemEventArgsConverter

The SelectedItemEventArgsConverter can be used as follows in XAML:

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
             x:Class="MyLittleApp.MainPage">
    <ContentPage.Resources>
         <ResourceDictionary>
             <toolkit:SelectedItemEventArgsConverter x:Key="SelectedItemEventArgsConverter" />
         </ResourceDictionary>
    </ContentPage.Resources>

     <VerticalStackLayout Padding="10">

        <Label
            Text="The SelectedItemEventArgsConverter is a converter that allows users to extract the SelectedItem value from an SelectedItemChangedEventArgs object. It can subsequently be used in combination with EventToCommandBehavior."
            TextColor="{StaticResource NormalLabelTextColor}"
            Margin="0, 0, 0, 20" />

        <ListView
            BackgroundColor="Transparent"
            ItemsSource="{Binding Items}"
            SelectedItem="{Binding ItemSelected, Mode=TwoWay}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <VerticalStackLayout Margin="6">
                            <Label Text="{Binding Name, StringFormat='Name: {0}'}"/>
                        </VerticalStackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
            <ListView.Behaviors>
                <toolkit:EventToCommandBehavior EventName="ItemSelected"
                                                Command="{Binding ItemSelectedCommand}"
                                                EventArgsConverter="{StaticResource SelectedItemEventArgsConverter}" />
            </ListView.Behaviors>
        </ListView>
    </VerticalStackLayout>
</ContentPage>

C#

The SelectedItemEventArgsConverter can be used as follows in C#:

class SelectedItemEventArgsConverterPage : ContentPage
{
    public SelectedItemEventArgsConverterPage()
    {
        var behavior = new EventToCommandBehavior
        {
            EventName = nameof(ListView.ItemSelected),
            EventArgsConverter = new SelectedItemEventArgsConverter()
        };
        behavior.SetBinding(EventToCommandBehavior.CommandProperty, nameof(ViewModel.ItemSelectedCommand);

        var listView = new ListView 
        { 
            HasUnevenRows = true 
        };
        listView.SetBinding(ListView.ItemsSource, nameof(ViewModel.Items));
        listView.Behaviors.Add(behavior);

        Content = listView;
    }
}

C# Markup

Our CommunityToolkit.Maui.Markup package provides a much more concise way to use this converter in C#.

using CommunityToolkit.Maui.Markup;

class SelectedItemEventArgsConverterPage : ContentPage
{
    public SelectedItemEventArgsConverterPage()
    {
        Content = new ListView
        {
            HasUnevenRows = true
        }
        .Bind(
            ListView.ItemsSourceProperty,
            static (ViewModel vm) => vm.Items)
        .Behaviors(
            new EventToCommandBehavior
            {
                EventName = nameof(ListView.ItemSelected),
                EventArgsConverter = new SelectedItemEventArgsConverter()
            }
            .Bind(
                EventToCommandBehavior.CommandProperty, 
                nameof(ViewModel.ItemTappedCommand)));                   
    }
}

Examples

You can find an example of this converter in action in the .NET MAUI Community Toolkit Sample Application.

API

You can find the source code for SelectedItemEventArgsConverter over on the .NET MAUI Community Toolkit GitHub repository.