public string Save(AssignCourse assignCourse)
        {
            if (assignGateway.IsCourseAssignExists(assignCourse))
            {
                return("Already Assigned");
            }

            else
            {
                int rowAffected = assignGateway.Save(assignCourse);
                if (rowAffected > 0)
                {
                    return("Course Assigned successfully");
                }
                return("Failed");
            }
        }