groupby query in C# linq

 var query = students.GroupBy(x => x.LastName)
                                .Select(g => g.FirstOrDefault())
                //.OrderByDescending(x => x.LastName)
                                .Select(x => new { lastName = x.LastName, fName = x.FirstName });

            var qqq = students.Select(s => s.LastName)
            .Distinct()
            .OrderByDescending(p => p)
            .Select(p => new { RR = p });


            var q = students.Where(x => x.LastName.Equals("Feng"));
            var q1 = students.GroupBy((x => x.LastName));

            Console.WriteLine("Group by a single property in an object:");

            var query1 =
                from s in students
                group s by s.LastName into newGroup
                orderby newGroup.Key
                select newGroup;

            foreach (var nameGroup in query1)
            {
                Console.WriteLine("Key: {0}", nameGroup.Key);
                foreach (var student in nameGroup)
                {
                    Console.WriteLine("\t{0}, {1}", student.LastName, student.FirstName);
                }
            }