代替了Htt presponseMessage IActionResult。并返回FileStreamResult，并得到了它的工作。

used IActionResult instead of HttpResponseMessage. And returned FileStreamResult, and got it working.

有一个新的问题，该文件是不是我从服务器流打开。但是，将创建一个新的问题。

Got a new problem, the file is not the one I open with the stream from server. But will create a new question for that.

继续： Asp.net 5的Web API返回的文件响应

感谢