using System;

using System.Collections.Generic;

using System.Linq;

​

public class Product

{

    public int Id { get; set; }

    public string Name { get; set; }

    public string Category { get; set; }

    public double Price { get; set; }

    public int Number { get; set; }

​

    public override string ToString() => $"Id: {Id} | Name: {Name} | Category: {Category} | Price: {Price} | Number: {Number}";

}

public class Program

{       

    public static void Main()

    {

        List<Product> productList = new()

        {

          new Product { Id = 1, Name = "Pasta", Category = "Beverages", Price = 18.0, Number = 39 },

          new Product { Id = 2, Name = "Anchius", Category = "Beverages", Price = 19.0, Number = 0 },

          new Product { Id = 3, Name = "Syrup", Category = "Condiments", Price = 10.0, Number = 13 },

          new Product { Id = 4, Name = "Seasoning", Category = "Condiments", Price = 22.0, Number = 53 },

          new Product { Id = 5, Name = "Gumbo", Category = "Condiments", Price = 21.35, Number = 41 },

          new Product { Id = 6, Name = "Spread", Category = "Condiments", Price = 25.0, Number = 120 },

          new Product { Id = 7, Name = "Dried", Category = "Confections", Price = 30.0, Number = 0 },

          new Product { Id = 8, Name = "Dried", Category = "Confections", Price = 16.0, Number = 14 },

          new Product { Id = 9, Name = "Sauce", Category = "Condiments", Price = 40.0, Number = 20 },

          new Product { Id = 10, Name = "Niku", Category = "Meat", Price = 97.0, Number = 29 },

          new Product { Id = 11, Name = "Niku", Category = "Meat", Price = 34.0, Number = 61 },

          new Product { Id = 12, Name = "Ragoo", Category = "Seafood", Price = 31.0, Number = 31 }

        };

        IDictionary<bool, IEnumerable<( string Category, IEnumerable<Product> Products)>> results = productList

            .GroupBy(

                product => product.Number == 0,

                ( isZero, products ) => ( 

                    NumberIsZero: isZero, 

                    ProductsByCategory: products.GroupBy(

                        product => product.Category,

                        ( category, products ) => ( category, products ))))

            .ToDictionary(item => item.NumberIsZero, item => item.ProductsByCategory);

​

        //var result1 = results[true];

        //var result2 = results[false];

​

        foreach (var result in results)

        {

            Console.WriteLine($"Products with Number {(result.Key ? "==" : "!=")} 0:");

​

            foreach (var entry in result.Value)

            {

                Console.WriteLine($"\t{entry.Category}:");

​

                foreach (var product in entry.Products)

                {

                    Console.WriteLine($"\t\t{product}");

                }

            }

        }

    }

}