How to: Perform Inner Joins

   http://msdn.microsoft.com/ru-ru/library/bb397941.aspx

class Person
        {
            public string FirstName { get; set; }
            public string LastName { get; set; }
        }

        class Pet
        {
            public string Name { get; set; }
            public Person Owner { get; set; }
        }

        /// <summary>
        /// Simple inner join.
        /// </summary>
        public static void InnerJoinExample()
        {
            Person magnus = new Person { FirstName = "Magnus", LastName = "Hedlund" };
            Person terry = new Person { FirstName = "Terry", LastName = "Adams" };
            Person charlotte = new Person { FirstName = "Charlotte", LastName = "Weiss" };
            Person arlene = new Person { FirstName = "Arlene", LastName = "Huff" };
            Person rui = new Person { FirstName = "Rui", LastName = "Raposo" };

            Pet barley = new Pet { Name = "Barley", Owner = terry };
            Pet boots = new Pet { Name = "Boots", Owner = terry };
            Pet whiskers = new Pet { Name = "Whiskers", Owner = charlotte };
            Pet bluemoon = new Pet { Name = "Blue Moon", Owner = rui };
            Pet daisy = new Pet { Name = "Daisy", Owner = magnus };

            // Create two lists.
            List<Person> people = new List<Person> { magnus, terry, charlotte, arlene, rui };
            List<Pet> pets = new List<Pet> { barley, boots, whiskers, bluemoon, daisy };

            // Create a collection of person-pet pairs. Each element in the collection
            // is an anonymous type containing both the person's name and their pet's name.
            var query = from person in people
                        join pet in pets on person equals pet.Owner
                        select new { OwnerName = person.FirstName, PetName = pet.Name };

            foreach (var ownerAndPet in query)
            {
                Console.WriteLine("\"{0}\" is owned by {1}", ownerAndPet.PetName, ownerAndPet.OwnerName);
            }
        }

        // This code produces the following output:
        //
        // "Daisy" is owned by Magnus
        // "Barley" is owned by Terry
        // "Boots" is owned by Terry
        // "Whiskers" is owned by Charlotte
        // "Blue Moon" is owned by Rui