问返回HttpResponseMessage的方法--如何返回异常，这可能吗？

EN

[HttpPost]
    public HttpResponseMessage SaveNewPdf(HttpRequestMessage req)
            {
                var json = req.Content.ReadAsStringAsync().Result;
                NewFile newFile = JsonConvert.DeserializeObject<NewFile>(json);
                string error = string.Empty;

                // check all the foreign key values to ensure they are valid
                var isArticleCategoryValid = HelperClasses.ForeignKeyChecks.IsArticleCategoryValid(newFile.ArticleCategory);
                var isDocumentTypeValid = HelperClasses.ForeignKeyChecks.IsDocumentTypeValid(newFile.DocumentType);
                var isActionPublisherValid = HelperClasses.ForeignKeyChecks.IsActionPublisherValid(newFile.ActionPublisher);
                var isRuleComplianceValid = HelperClasses.ForeignKeyChecks.IsRuleComplianceValid(newFile.RuleCompliance);

                if (!isArticleCategoryValid)
                {
                    error = "articleCategory in the JSON is not a valid Article Category";
                    return new HttpResponseException();
                }
    }