Mini Kabibi Habibi

using System;
using System.Collections;
using System.Linq;
using System.Web.UI;
using DevExpress.Web.Demos.Models;

namespace DevExpress.Web.Demos {
    public abstract class ItemsData: IHierarchicalEnumerable, IEnumerable {
        public ItemsData() {
        }

        public abstract IEnumerable Data { get; }

        public IEnumerator GetEnumerator() {
            return Data.GetEnumerator();
        }
        public IHierarchyData GetHierarchyData(object enumeratedItem) {
            return (IHierarchyData)enumeratedItem;
        }
    }

    public class ItemData: IHierarchyData {
        public string Text { get; protected set; }
        public string NavigateUrl { get; protected set; }

        public ItemData(string text, string navigateUrl) {
            Text = text;
            NavigateUrl = navigateUrl;
        }

        // IHierarchyData
        bool IHierarchyData.HasChildren {
            get { return HasChildren(); }
        }
        object IHierarchyData.Item {
            get { return this; }
        }
        string IHierarchyData.Path {
            get { return NavigateUrl; }
        }
        string IHierarchyData.Type {
            get { return GetType().ToString(); }
        }
        IHierarchicalEnumerable IHierarchyData.GetChildren() {
            return CreateChildren();
        }
        IHierarchyData IHierarchyData.GetParent() {
            return null;
        }

        protected virtual bool HasChildren() {
            return false;
        }
        protected virtual IHierarchicalEnumerable CreateChildren() {
            return null;
        }
    }


    public class CategoriesData: ItemsData {
        public override IEnumerable Data {
            get { return from category in NorthwindDataProvider.DB.Categories select new CategoryData(category); }
        }
    }

    public class CategoryData: ItemData {
        public Category Category { get; protected set; }

        public CategoryData(Category category)
            : base(category.CategoryName, "?CategoryID=" + category.CategoryID) {
            Category = category;
        }

        protected override bool HasChildren() {
            return true;
        }
        protected override IHierarchicalEnumerable CreateChildren() {
            return new ProductsData(Category.CategoryID);
        }
    }

    public class ProductsData: ItemsData {
        public int CategoryID { get; protected set; }

        public ProductsData(int categoryID)
            : base() {
            CategoryID = categoryID;
        }

        public override IEnumerable Data {
            get { return from product in NorthwindDataProvider.DB.Products where product.CategoryID == CategoryID select new ProductData(product); }
        }
    }

    public class ProductData: ItemData {
        public ProductData(Product product)
            : base(product.ProductName, "?CategoryID=" + product.CategoryID + "&ProductID=" + product.ProductID) {
        }
    }
}