public IActionResult Create([FromBody] AddEditMaterialModel model)
        {
            // map model to entity
            var courseMaterial = _mapper.Map <CourseMaterial>(model);

            try
            {
                _courseMaterialService.Create(courseMaterial);
                return(Ok());
            }
            catch (AppException ex)
            {
                // return error message if there was an exception
                return(BadRequest(new { message = ex.Message }));
            }
        }
        public IActionResult Update(int id, [FromBody] AddEditMaterialModel model)
        {
            // map model to entity and set id
            var courseMaterial = _mapper.Map <CourseMaterial>(model);

            courseMaterial.Id = id;

            try
            {
                // update course material
                _courseMaterialService.Update(courseMaterial);
                return(Ok());
            }
            catch (AppException ex)
            {
                // return error message if there was an exception
                return(BadRequest(new { message = ex.Message }));
            }
        }