How to notify item selection using MVVM in Xamarin.Forms ListView?

This example demonstrates how to notify item selection using MVVM in Xamarin.Forms listview.

Sample

<Grid>
    <listView:SfListView x:Name="listView" ItemSize="70" ItemSpacing="0,0,5,0"
                    ItemsSource="{Binding contactsinfo}" IsStickyHeader="True" TapCommand="{Binding }"
                    SelectionMode="Multiple" IsStickyGroupHeader="True" GroupHeaderSize="50">
                <listView:SfListView.Behaviors>
                    <local:EventToCommandBehavior EventName="SelectionChanged" 
                                        Command="{Binding SelectionChangedCommand}"
                                        Converter="{StaticResource EventArgs}" />
                </listView:SfListView.Behaviors>
        <listView:SfListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <ViewCell.View>
                        <Grid x:Name="grid" RowSpacing="1">
                            <code>
                            . . .
                            . . .
                            <code>
                        </Grid>
                    </ViewCell.View>
                </ViewCell>
            </DataTemplate>
        </listView:SfListView.ItemTemplate>
    </listView:SfListView>
</Grid>

ViewModel.cs:
Command<object> selectionChangedCommand;

public Command<object> SelectionChangedCommand
{
    get { return selectionChangedCommand; }
    protected set { selectionChangedCommand = value; }
}

public ObservableCollection<Contacts> contactsinfo { get; set; }

public ContactsViewModel()
{
    selectionChangedCommand = new Command<object>(OnSelectionChanged);
    contactsinfo = new ObservableCollection<Contacts>();
    Random r = new Random();
    foreach (var cusName in CustomerNames)
    {
        var contact = new Contacts(cusName, r.Next(720, 799).ToString() + " - " + r.Next(3010, 3999).ToString());
        contact.ContactImage = ImageSource.FromResource("PassItemData.Images.Image" + r.Next(0, 28) + ".png");
        contactsinfo.Add(contact);
    }
}

public void OnSelectionChanged(object obj)
{
    var eventArgs = obj as ItemSelectionChangedEventArgs;

    for (int i = 0; i < eventArgs.RemovedItems.Count; i++)
    {
        var item = eventArgs.RemovedItems[i] as Contacts;
        if (item.IsSelected)
        {
            item.IsSelected = false;
            App.Current.MainPage.DisplayAlert("Message", "Item removed from selected item", "ok");
        }
    }
    for (int i = 0; i < eventArgs.AddedItems.Count; i++)
    {
        var item = eventArgs.AddedItems[i] as Contacts;
        if (!item.IsSelected)
        {
            item.IsSelected = true;
            App.Current.MainPage.DisplayAlert("Message", "Item added into selected item", "ok");
        }
    }
}

See How to notify item selection using MVVM in Xamarin.Forms ListView for more details.

Requirements to run the demo

• Visual Studio 2017 or Visual Studio for Mac
• Xamarin add-ons for Visual Studio (available via the Visual Studio installer).

Troubleshooting

Path too long exception

If you are facing path too long exception when building this example project, close Visual Studio and rename the repository to short and build the project.