class CustomJoins
    {

        #region Data

        class Product
        {
            public string Name { get; set; }
            public int CategoryID { get; set; }
        }

        class Category
        {
            public string Name { get; set; }
            public int ID { get; set; }
        }

        // Specify the first data source.
        List<Category> categories = new List<Category>()
        { 
            new Category(){Name="Beverages", ID=001},
            new Category(){ Name="Condiments", ID=002},
            new Category(){ Name="Vegetables", ID=003},         
        };

        // Specify the second data source.
        List<Product> products = new List<Product>()
       {
          new Product{Name="Tea",  CategoryID=001},
          new Product{Name="Mustard", CategoryID=002},
          new Product{Name="Pickles", CategoryID=002},
          new Product{Name="Carrots", CategoryID=003},
          new Product{Name="Bok Choy", CategoryID=003},
          new Product{Name="Peaches", CategoryID=005},
          new Product{Name="Melons", CategoryID=005},
          new Product{Name="Ice Cream", CategoryID=007},
          new Product{Name="Mackerel", CategoryID=012},
        };
        #endregion

        static void Main()
        {
            CustomJoins app = new CustomJoins();
            app.CrossJoin();
            app.NonEquijoin();

            Console.WriteLine("Press any key to exit.");
            Console.ReadKey();
        }

        void CrossJoin()
        {
            var crossJoinQuery = 
                from c in categories
                from p in products
                select new { c.ID, p.Name };

            Console.WriteLine("Cross Join Query:");
            foreach (var v in crossJoinQuery)
            {
                Console.WriteLine("{0,-5}{1}", v.ID, v.Name);
            }            
        }

        void NonEquijoin()
        {
            var nonEquijoinQuery = 
                from p in products
                let catIds = from c in categories
                             select c.ID
                where catIds.Contains(p.CategoryID) == true
                select new { Product = p.Name, CategoryID = p.CategoryID };

            Console.WriteLine("Non-equijoin query:");
            foreach (var v in nonEquijoinQuery)
            {
                Console.WriteLine("{0,-5}{1}",  v.CategoryID, v.Product);
            }
        }
    }
    /* Output:
Cross Join Query:
1    Tea
1    Mustard
1    Pickles
1    Carrots
1    Bok Choy
1    Peaches
1    Melons
1    Ice Cream
1    Mackerel
2    Tea
2    Mustard
2    Pickles
2    Carrots
2    Bok Choy
2    Peaches
2    Melons
2    Ice Cream
2    Mackerel
3    Tea
3    Mustard
3    Pickles
3    Carrots
3    Bok Choy
3    Peaches
3    Melons
3    Ice Cream
3    Mackerel
Non-equijoin query:
1    Tea
2    Mustard
2    Pickles
3    Carrots
3    Bok Choy
Press any key to exit.
     */

class MergeTwoCSVFiles : StudentClass
{
    static void Main()
    {
        string[] names = System.IO.File.ReadAllLines(@"../../../names.csv");
        string[] scores = System.IO.File.ReadAllLines(@"../../../scores.csv");

        // Merge the data sources using a named type
        // var could be used instead of an explicit type
        IEnumerable<Student> queryNamesScores =
            from name in names
            let x = name.Split(',')
            from score in scores
            let s = score.Split(',')
            where x[2] == s[0]
            select new Student()
            {
                FirstName = x[0],
                LastName = x[1],
                ID = Convert.ToInt32(x[2]),
                ExamScores = (from scoreAsText in s.Skip(1)
                              select Convert.ToInt32(scoreAsText)).
                              ToList()
            };

        // Optional. Store the newly created student objects in memory
        // for faster access in future queries
        List<Student> students = queryNamesScores.ToList();

        foreach (var student in students)
        {
            Console.WriteLine("The average score of {0} {1} is {2}.",
                student.FirstName, student.LastName, student.ExamScores.Average());
        }

        //Keep console window open in debug mode
        Console.WriteLine("Press any key to exit.");
        Console.ReadKey();
    }
}
/* Output: 
    The average score of Adams Terry is 85.25.
    The average score of Fakhouri Fadi is 92.25.
    The average score of Feng Hanying is 88.
    The average score of Garcia Cesar is 88.25.
    The average score of Garcia Debra is 67.
    The average score of Garcia Hugo is 85.75.
    The average score of Mortensen Sven is 84.5.
    The average score of O'Donnell Claire is 72.25.
    The average score of Omelchenko Svetlana is 82.5.
    The average score of Tucker Lance is 81.75.
    The average score of Tucker Michael is 92.
    The average score of Zabokritski Eugene is 83.
 */