public class ThingSale
    {
        private static List<string> Categories = new List<string> { "Music", "Video", "Books", "Electronics", "Computers & Tablets" };
        private static Dictionary<string, List<string>> AllCategories = new Dictionary<string, List<string>>();
        public string Category { get; set; }

        public double? Sales { get; set; }
        public List<ThingSale> Items { get; set; }

        public static void EnsureInitAllCategories()
        {
            if (AllCategories.Count > 0)
            {
                return;
            }

            AllCategories.Add("Music", new List<string> { "Country", "Rock", "Classical", "Soundtracks", "Jazz", "Electronic" });
            AllCategories.Add("Country", new List<string> { "Classic Country", "Cowboy Country", "Outlaw Country", "Western Swing", "Roadhouse Country" });
            AllCategories.Add("Rock", new List<string> { "Hard Rock", "Blues Rock", "Funk Rock", "Rap Rock", "Guitar Rock", "Progressive Rock" });
            AllCategories.Add("Classical", new List<string> { "Symphonies", "Chamber Music" });
            AllCategories.Add("Soundtracks", new List<string> { "Movie Soundtracks", "Musical Soundtracks" });
            AllCategories.Add("Jazz", new List<string> { "Smooth Jazz", "Vocal Jazz", "Jazz Fusion", "Swing Jazz", "Cool Jazz", "Traditional Jazz" });
            AllCategories.Add("Electronic", new List<string> { "Electronica", "Disco", "House" });

            AllCategories.Add("Video", new List<string> { "Movie", "TV" });
            AllCategories.Add("Movie", new List<string> { "Kid & Family", "Action & Adventure", "Animation", "Comedy", "Drama", "Romance" });
            AllCategories.Add("TV", new List<string> { "Science Fiction", "Documentary", "Fantasy", "Military & War", "Horror" });

            AllCategories.Add("Books", new List<string> { "Arts & Photography", "Children's Books", "History", "Mystery", "Romance", "Sci-Fi & Fantasy" });
            AllCategories.Add("Arts & Photography", new List<string> { "Architecture", "Graphic Design", "Drawing", "Photography", "Performing Arts" });
            AllCategories.Add("Children's Books", new List<string> { "Beginning Readers", "Board Books", "Chapter Books", "Coloring Books", "Picture Books", "Sound Books" });
            AllCategories.Add("History", new List<string> { "Ancient", "Medieval", "Renaissance" });
            AllCategories.Add("Mystery", new List<string> { "Thriller & Suspense", "Mysteries" });
            AllCategories.Add("Romance", new List<string> { "Action & Adventure", "Holidays", "Romantic Comedy", "Romantic Suspense", "Western", "Historical" });
            AllCategories.Add("Sci-Fi & Fantasy", new List<string> { "Fantasy", "Gaming", "Science Fiction" });

            AllCategories.Add("Electronics", new List<string> { "Camera", "Headphones", "Cell Phones", "Wearable Technology" });
            AllCategories.Add("Camera", new List<string> { "Digital Cameras", "Film Photography", "Lenses", "Video", "Accessories" });
            AllCategories.Add("Headphones", new List<string> { "Earbud headphones", "Over-ear headphones", "On-ear headphones", "Bluetooth headphones", "Noise-cancelling headphones", "Audiophile headphones" });
            AllCategories.Add("Cell Phones", new List<string> { "Cell Phone", "Accessories" });
            AllCategories.Add("Accessoriess", new List<string> { "Batteries", "Bluetooth Headsets", "Bluetooth Speakers", "Chargers", "Screen Protectors" });
            AllCategories.Add("Wearable Technology", new List<string> { "Activity Trackers", "Smart Watches", "Sports & GPS Watches", "Virtual Reality Headsets", "Wearable Cameras", "Smart Glasses" });

            AllCategories.Add("Computers & Tablets", new List<string> { "Desktops", "Laptops", "Tablets" });
            AllCategories.Add("Desktops", new List<string> { "All-in-ones", "Minis", "Towers" });
            AllCategories.Add("Laptops", new List<string> { "2 in 1 laptops", "Traditional laptops" });
            AllCategories.Add("Tablets", new List<string> { "IOS", "Andriod", "Fire OS", "Windows" });
        }
        public static IEnumerable<ThingSale> GetData()
        {
            EnsureInitAllCategories();
            var result = new List<ThingSale>();
            Categories.ForEach(cat =>
            {
                result.Add(Create(cat));
            });

            return result;
        }

        private static ThingSale Create(string category)
        {
            var rand = new Random(0);
            var item = new ThingSale { Category = category };
            if (!AllCategories.ContainsKey(category))
            {
                item.Sales = rand.NextDouble() * 100;
            }
            else
            {
                item.Items = new List<ThingSale>();
                AllCategories[category].ForEach(subCat =>
                {
                    item.Items.Add(Create(subCat));
                });
            }
            return item;
        }
    }

public partial class ViewController : UIViewController
    {
        C1TreeMap treeMap;
        public ViewController (IntPtr handle) : base (handle)
        {
        }
        public override void ViewDidLoad ()
        {
            base.ViewDidLoad ();
            treeMap = new C1TreeMap();
            treeMap.ChartType = C1.iOS.Chart.TreeMapType.Squarified;
            treeMap.Binding = "sales";
            treeMap.BindingName = "type";
            treeMap.MaxDepth = 2;
            treeMap.ChildItemsPath = "items";
            treeMap.ItemsSource = SalesData.CreateHierarchicalData();
            this.Add(treeMap);

            treeMap.DataLabel = new ChartDataLabel() { Content = "{}{type}", Position = ChartLabelPosition.Center };
            treeMap.DataLabel.Style.FontSize = 10;
        }

        public override void ViewDidLayoutSubviews()
        {
            base.ViewDidLayoutSubviews();
            treeMap.Frame = new CGRect(this.View.Frame.X, this.View.Frame.Y + 80,
                                     this.View.Frame.Width, this.View.Frame.Height - 80);
        }
    }