webapi返回不帶引號的字符串，解決自動加雙引號的問題

返回類型改為HttpResponseMessage類型

[Route("api/TestControllers/test")]
[HttpGet]
public HttpResponseMessage Test()
{
    HttpResponseMessage responseMessage = new HttpResponseMessage { Content = new StringContent("你要返回的字符串", Encoding.GetEncoding("UTF-8"), "text/plain") };
         
    return responseMessage;
}