javascript - Error on Downloading From using Asp.net web api -

i'm using code below downloading web api in asp.net. when i'm trying click download button, calls api. after executing "downloadfile"-function, download dialog box isn't coming .

[httpget]

    public httpresponsemessage downloadfile(string downloadfilepath)     {          httpresponsemessage result = null;         var localfilepath = httpcontext.current.server.mappath(downloadfilepath);          // check if parameter valid         if (string.isnullorempty(downloadfilepath))         {             result = request.createresponse(httpstatuscode.badrequest);         }         // check if file exists on server         else if (!file.exists(localfilepath))         {             result = request.createresponse(httpstatuscode.gone);         }         else         {// serve file client             result = request.createresponse(httpstatuscode.ok);             result.content = new streamcontent(new filestream(localfilepath, filemode.open, fileaccess.read));             result.content.headers.contentdisposition = new system.net.http.headers.contentdispositionheadervalue("attachment");             result.content.headers.contentdisposition.filename = downloadfilepath;         }          return result;         } 

i didn't exception code above, dialog box downloading file isn't coming.

here code, using , works great. hope give idea

.... var filebytes = helper.getfilebytes(filepath);//convert file bytes                     var stream = new memorystream(filebytes);                     resp.content = new streamcontent(stream);                     resp.content.headers.contenttype = new mediatypeheadervalue("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");                     resp.content.headers.contentdisposition = new contentdispositionheadervalue("attachment") { filename = filerequest.filename };                     resp.content.headers.add("content-encoding", "utf-8");                                    return resp; 

and, here code getfilebytes method,

public static byte[] getfilebytes(string filepath)         {             var fileinfo = new fileinfo(filepath);             if (fileinfo.exists)             {                 return file.readallbytes(fileinfo.fullname);             }             return null;                    }