using System.ComponentModel;
using System.Collections.ObjectModel;

namespace ClientUI.Samples.Models
{
    public class Category : INotifyPropertyChanged
    {
        private string _categoryName;
        private ObservableCollection<Product> _products;

        public string CategoryName
        {
            get { return this._categoryName; }
            set
            {
                if (this._categoryName != value)
                {
                    this._categoryName = value;
                    this.OnPropertyChanged("CategoryName");
                }
            }
        }

        public ObservableCollection<Product> Products
        {
            get { return this._products; }
            set
            {
                if (this._products != value)
                {
                    this._products = value;
                    this.OnPropertyChanged("Products");
                }
            }
        }

        protected void OnPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
            {
                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

using System.ComponentModel;
using System.Windows.Media;

namespace ClientUI.Samples.Models
{
    public class Product : INotifyPropertyChanged
    {
        private string _productName;
        
        public string ProductName
        {
            get { return this._productName; }
            set
            {
                if (this._productName != value)
                {
                    this._productName = value;
                    this.OnPropertyChanged("ProductName");
                }
            }
        }

        protected void OnPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
            {
                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

using System.Collections.ObjectModel;
using System.ComponentModel;
using ClientUI.Samples.Models;

namespace ClientUI.Samples.ViewModels
{
    public class MainPageViewModel : INotifyPropertyChanged
    {
        public MainPageViewModel()
        {
            this.Data = new ObservableCollection<Category>();

            Category beverages = new Category();
            beverages.CategoryName = "Beverages";
            beverages.Products = new ObservableCollection<Product>();
            beverages.Products.Add(new Product() { ProductName = "Chai" });
            beverages.Products.Add(new Product() { ProductName = "Chang" });
            beverages.Products.Add(new Product() { ProductName = "Sasquatch Ale" });
            beverages.Products.Add(new Product() { ProductName = "Ipoh Coffee" });

            Category seafood = new Category();
            seafood.CategoryName = "Seafood";
            seafood.Products = new ObservableCollection<Product>();
            seafood.Products.Add(new Product() { ProductName = "Ikura" });
            seafood.Products.Add(new Product() { ProductName = "Konbu" });
            seafood.Products.Add(new Product() { ProductName = "Carnarvon Tigers" });
            seafood.Products.Add(new Product() { ProductName = "Escargots de Bourgogne" });

            this.Data.Add(beverages);
            this.Data.Add(seafood);

        }

        private ObservableCollection<Category> _data;

        public ObservableCollection<Category> Data
        {
            get { return this._data; }
            set
            {
                if (this._data != value)
                {
                    this._data = value;
                    this.OnPropertyChanged("Data");
                }
            }
        }

        protected void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;

            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}