public async Task<IHttpActionResult> PutCourse(int id, Course course)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (id != course.CourseId)
            {
                return BadRequest();
            }

            db.Entry(course).State = EntityState.Modified;

            try
            {
                await db.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!CourseExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return StatusCode(HttpStatusCode.NoContent);
        }
        public async Task<IHttpActionResult> PostCourse(Course course)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            db.Courses.Add(course);
            await db.SaveChangesAsync();

            return CreatedAtRoute("DefaultApi", new { id = course.CourseId }, course);
        }