DetailPage.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;

namespace DrilldownListViewDemoVS
{
    class DetailPage : ContentPage
    {
        public DetailPage(ListItem item)
        {
            Label titleLabel = new Label
            {
                Text = item.Title,
                FontSize = 40
            };

            Label descriptionLabel = new Label
            {
                Text = item.Description,
                FontSize = 40
            };

            var stackLayout = new StackLayout
            {
                Children = { titleLabel, descriptionLabel }
            };

            this.Content = stackLayout;
        }
    }
}