using System;

using System.Collections.Generic;

using System.Linq;

​

    // 1. Write a LINQ query:

    // Select all the customers who have a productId.

    // Ignore anyone who does not have a customer Id.

    // Ignore anyone over 18

    // Group the children by Gender, showing their Last Name,

    // The results should order "F" first and "M" second.

    // 2. Print the result in two rows, 

    // with the last names comma delimited

    // The output should look like this:

    // F  Smith

    // M  Jones,Hills

​

    // While LINQ is preferred, if you do not 

    // know LINQ, then you may write the answer

    // using SQL Pseudocode.

​

​

namespace TestConsoleApp

{

    public class Program

    {

        public static void Main(string[] args)

        {

            var productAId = Guid.NewGuid();

            var productBId = Guid.NewGuid();

            var customers = new List<Customer>

            {

                new Customer {Id = Guid.NewGuid(), Gender="F", LastName = "Adams", Age = 50, ProductId=productAId},

                new Customer {Id = Guid.NewGuid(), Gender="M", LastName = "Jones", Age = 10, ProductId=productAId},   

                new Customer {Id = Guid.NewGuid(), Gender="M", LastName = "Hills", Age = 17, ProductId=productBId},

                new Customer {Id = Guid.Empty, LastName = string.Empty, Age = 0},

                new Customer {Id = Guid.NewGuid(), Gender="F", LastName = "Smith", Age = 15, ProductId=productAId}              

            };

            var products = new List<Product>

            {

                new Product {Id = productBId, Name="ProdB", Description = "Product B"},

                new Product {Id = productAId, Name="ProdA", Description = "Product B"}

            };

​

            var coreDemographic = from cust in customers where cust.Age < 18 && cust.ProductId != null && cust.Id != Guid.Empty group cust by cust.Gender into genderGroup orderby genderGroup.Key select genderGroup;

​

                // 1. Write the linq query here.                            

​

            foreach( var c in coreDemographic)

            {

                Console.Write(c.Key + "  ");

                int i = 0;

                foreach (var person in c)

                {

                    if (i > 0)

                    {

                        Console.Write(", ");

                    }

                    Console.Write(person.LastName);

                    i++;

                }

                Console.WriteLine("");

                // 2. print here.

            }           

        }

​

        public class Customer

        {

            public Guid Id { get; set; }

            public string LastName { get; set; }

            public int Age { get; set; }

            public string Gender {get; set;}

            public Guid? ProductId {get; set;}

        }

        public class Product

        {

            public Guid Id { get; set; }

            public string Name { get; set; }

            public string Description { get; set; }         

        }

    }

​

}