public IHttpActionResult Post(StudentRequestModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var student = new Student
            {
                FirstName = model.FirstName,
                LastName = model.LastName,
                Age = model.Age,
                Number = model.Number
            };

            this.data.Students.Add(student);
            this.data.Students.SaveChanges();

            return this.Ok(student);
        }
        public IHttpActionResult Put(int id, StudentRequestModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var student = this.data.Students
                .All()
                .FirstOrDefault(s => s.Id == id);

            if (student == null)
            {
                return this.BadRequest("Student with id " + id + " does not exist!");
            }

            student.FirstName = model.FirstName;
            student.LastName = model.LastName;
            student.Age = model.Age;
            student.Number = model.Number;

            this.data.Students.Update(student);
            this.data.Students.SaveChanges();

            return this.Ok(model);
        }