public IHttpActionResult AddCourse(CourseDTO c)
        {
            //checking if the course being added is not of the right data type
            if (c == null)
            {
                throw new HttpResponseException(HttpStatusCode.PreconditionFailed);
            }

            //setting location url
            var location = Url.Link("GetCourse", new { id = c.ID });

            //adding course to list
            //_courses.Add(c);

            return Created(location, c);
        }
        public IHttpActionResult UpdateCourse(int id, CourseDTO course)
        {
            //checking if the course being added is not of the right data type
            if (course == null)
            {
                throw new HttpResponseException(HttpStatusCode.PreconditionFailed);
            }

            //update right course
            /*
            foreach (CourseDTO c in _courses)
            {
                if (c.ID == id)
                {
                    var temp = _courses.SingleOrDefault(x=>x.ID == course.ID);
                    temp.Name = course.Name;
                    temp.StartDate = course.StartDate;
                    temp.EndDate = course.EndDate;

                    //201 successfully created
                    var location = Url.Link("GetCourse", new { id = course.ID });
                    return Created(location, temp);
                }
            }*/

            //404 id not found
            return NotFound();
        }