public void UploadImg(HttpContext context)
 {
     if (context.Request.Files.Count > 0)
     {
         var imgSrc = SerializeHelp.UploadFile(context);
         var res    = new { msg = "ok", code = 0, src = imgSrc };
         context.Response.Write(SerializeHelp.ToJson(res));
     }
     else
     {
         var res = new { msg = "no", code = 500, src = "" };
         context.Response.Write(res);
     }
 }