private ICollection <UserEntity> SetBuyItemAnnouncementReceivers(string senderId)
        {
            var senderCourses = _courseOfStudyService.GetStudentCourses(senderId);
            var receivers     = new List <UserEntity>();

            foreach (var course in senderCourses)
            {
                var sameCourses = _studentExchangeDataContext.CoursesOfStudy.Include(c => c.Groups)
                                  .Include(c => c.Faculty).ToList().FindAll(c => c.Faculty.Id == course.Faculty.Id && c.Name == course.Name);
                var yearFilteredCourses = sameCourses.Where(c => int.Parse(c.StartYear) <= int.Parse(course.StartYear));
                foreach (var fcourse in yearFilteredCourses)
                {
                    foreach (var group in fcourse.Groups)
                    {
                        receivers.AddRange(group.Students);
                    }
                }
            }
            receivers.RemoveAll(r => r.Id == senderId);
            return(receivers.Distinct().ToList());
        }
 public IHttpActionResult GetStudentCourses(string studentId)
 {
     return(Content(HttpStatusCode.OK, _courseOfStudyService.GetStudentCourses(studentId)));
 }