"Case when" in Linq

using (EntityModel obj = new EntityModel())

            {

                var query = from grade in obj.StudentGrade

                                join student in obj.Person on grade.Person.PersonID

                                equals student.PersonID

                                select new

                               {

                                  FirstName = student.FirstName,

                                  LastName = student.LastName,

                                  Grade = grade.Grade.Value >= 4 ? "A" :

                                             grade.Grade.Value >= 3 ? "B" :

                                             grade.Grade.Value >= 2 ? "C" :

                                             grade.Grade.Value != null ? "D" : "-"

                               };

 

                foreach (var q in query)

                {

                    Console.WriteLine("{0} {1} has {2} grade", q.FirstName,
                                              q.LastName, q.Grade);

                }

                Console.Read();

            } 

Enjoy............