在返回HTTPResponseMessage时,需要指定返回的内容类型为"application/pdf"。以下是示例代码:
public HttpResponseMessage GetPdfFile()
{
var fileStream = new FileStream("file.pdf", FileMode.Open);
var result = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StreamContent(fileStream)
};
result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
return result;
}