public class Animal
{
        public string Name { get; set; }
        public string Location { get; set; }
        public string Details { get; set; }
        public string ImageUrl { get; set; }
}

namespace XF_ShellApp.Data
{
    public static class CachorrosData
    {
        public static IList<Animal> Cachorros { get; private set; }

        static CachorrosData()
        {
            Cachorros = new List<Animal>();

            Cachorros.Add(new Animal
            {
                Name = "Afghan Hound",
                Location = "Afghanistan",
                Details = "The Afghan Hound is a hound that is distinguished by its thick, fine, silky coat and its tail with a ring curl at the end. The breed is selectively bred for its unique features in the cold mountains of Afghanistan.  Other names for this breed are Kuchi Hound, Tāzī, Balkh Hound, Baluchi Hound, Barakzai Hound, Shalgar Hound, Kabul Hound, Galanday Hound or sometimes incorrectly African Hound.",
                ImageUrl = "https://upload.wikimedia.org/wikipedia/commons/6/69/Afghane.jpg"
            });

            Cachorros.Add(new Animal
            {
                Name = "Alpine Dachsbracke",
                Location = "Austria",
                Details = "The Alpine Dachsbracke is a small breed of dog of the scent hound type originating in Austria. The Alpine Dachsbracke was bred to track wounded deer as well as boar, hare, and fox. It is highly efficient at following a trail even after it has gone cold. The Alpine Dachsbracke is very sturdy, and Austria is said to be the country of origin.",
                ImageUrl = "https://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Alpejski_gończy_krótkonożny_g99.jpg/320px-Alpejski_gończy_krótkonożny_g99.jpg"
            });

            Cachorros.Add(new Animal
            {
                Name = "American Bulldog",
                Location = "United States",
                Details = "The American Bulldog is a breed of utility dog descended from the Old English Bulldog.",
                ImageUrl = "https://upload.wikimedia.org/wikipedia/commons/5/5e/American_Bulldog_600.jpg"
            });

            Cachorros.Add(new Animal
            {
                Name = "Bearded Collie",
                Location = "Scotland",
                Details = "The Bearded Collie, or Beardie, is a herding breed of dog once used primarily by Scottish shepherds, but now mostly a popular family companion. Bearded Collies have an average weight of 18–27 kilograms (40–60 lb). Males are around 51–56 centimetres (20–22 in) tall at the withers while females are around 51–53 centimetres (20–21 in) tall.",
                ImageUrl = "https://upload.wikimedia.org/wikipedia/commons/9/9c/Bearded_Collie_600.jpg"
            });
        }
    }
}

<?xml version="1.0" encoding="utf-8" ?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             x:Class="XF_ShellApp.App">
    <Application.Resources>
        <DataTemplate x:Key="AnimalTemplate">
            <Grid Padding="10">
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto" />
                    <ColumnDefinition Width="Auto" />
                </Grid.ColumnDefinitions>
                <Image Grid.RowSpan="2" 
                       Source="{Binding ImageUrl}" 
                       Aspect="AspectFill"
                       HeightRequest="80" 
                       WidthRequest="80" />
                <Label Grid.Column="1" 
                       Text="{Binding Name}" 
                       FontAttributes="Bold" />
                <Label Grid.Row="1"
                       Grid.Column="1" 
                       Text="{Binding Location}"
                       FontAttributes="Italic" 
                       VerticalOptions="End" />
            </Grid>
        </DataTemplate>
    </Application.Resources>
</Application>

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:data="clr-namespace:XF_ShellApp.Data"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             x:Class="XF_ShellApp.Views.Caes">

    <CollectionView Margin="20"
                    ItemsSource="{x:Static data:CachorrosData.Cachorros}"
                    ItemTemplate="{StaticResource AnimalTemplate}"
                    SelectionMode="Single"
                    SelectionChanged="OnCollectionViewSelectionChanged" />

</ContentPage>

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace XF_ShellApp.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class Caes : ContentPage
    {
        public Caes()
        {
            InitializeComponent();
        }

        void OnCollectionViewSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
           //a declarar
        }
    }
}