C#LINK

 var students = new[]
            {
                new {LName="Jones",FName="Mary",Age=23, Major="History"},
                new {LName="Smith",FName="Bob",Age=20, Major="Comsci"},
                new {LName="Fleming",FName="Carol",Age=21, Major="History"}
            };
            //var query = from student in students
            //            orderby student.Age
            //            select student.LName;
            var query = from student in students
                        group student by student.Major;

            foreach(var a in query)
            {
                Console.WriteLine("{0}",a.Key);//a.Key分组键
                foreach(var t in a)
                    Console.WriteLine("      {0},{1}",t.LName,t.FName);
            }
            Console.ReadKey();

            var groupA = new[] { 3, 4, 5, 6 };
            var groupB = new[] { 6, 7, 8, 9 };
            var someInts = from a in groupA
                           from b in groupB
                           let num = a + b
                           where num >= 11
                           where a != 4
                           select new { a, b, num };
            foreach (var a in someInts)
            {
                Console.WriteLine(a);
            }
            Console.ReadKey();