webapi下载文件

[HttpGet]
public IHttpActionResult ExportData()
{ ...
var dt = ExcelHelper.ListToDataTable(list);
var fileName = SysConfig.WebTempPath + Guid.NewGuid().ToString() + ".xls";
ExcelHelper.ExportToFile(dt,fileName);

//http://www.cnblogs.com/enternal/p/5417519.html
HttpResponseMessage httpResponseMessage = new HttpResponseMessage(HttpStatusCode.OK);
FileStream fileStream = File.OpenRead(fileName);
httpResponseMessage.Content = new StreamContent(fileStream);
httpResponseMessage.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
httpResponseMessage.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
{
FileName =HttpUtility.UrlEncode(Path.GetFileName(fileName))
}; return ResponseMessage(httpResponseMessage); }