public void QueryNestedGroups()

{

    var queryNestedGroups =

        from student in students

        group student by student.Year into newGroup1

        from newGroup2 in

            (from student in newGroup1

             group student by student.LastName)

        group newGroup2 by newGroup1.Key;

    // Three nested foreach loops are required to iterate

    // over all elements of a grouped group. Hover the mouse

    // cursor over the iteration variables to see their actual type.

    foreach (var outerGroup in queryNestedGroups)

    {

        Console.WriteLine($"DataClass.Student Level = {outerGroup.Key}");

        foreach (var innerGroup in outerGroup)

        {

            Console.WriteLine($"\tNames that begin with: {innerGroup.Key}");

            foreach (var innerGroupElement in innerGroup)

            {

                Console.WriteLine("\t\t{innerGroupElement.LastName} {innerGroupElement.FirstName}");

            }

        }

    }

}