public IActionResult RemoveStudentFromGroup(Guid groupId, Guid studentId)
        {
            var user = _usersRepository.GetByIdAsync(studentId).Result;

            if (user == null || user.Id != studentId)
            {
                return(NotFound());
            }

            var group = _groupsRepository.GetByIdAsync(groupId).Result;

            if (group == null)
            {
                return(NotFound());
            }

            var removeStudentFromGroupViewModel = new RemoveStudentFromGroupViewModel {
                GroupId     = groupId,
                StudentId   = studentId,
                StudentName = user.UserName,
                GroupName   = group.Name
            };

            return(View(removeStudentFromGroupViewModel));
        }
        public async Task <IActionResult> RemoveStudentFromGroupConfirmed(RemoveStudentFromGroupViewModel removeStudentFromGroupViewModel)
        {
            var deleted = await _groupsRepository
                          .DeleteStudentAsync(removeStudentFromGroupViewModel.GroupId, removeStudentFromGroupViewModel.StudentId);

            if (!deleted)
            {
                return(NotFound());
            }

            return(RedirectToAction(nameof(Edit), new { id = removeStudentFromGroupViewModel.GroupId }));
        }