title: Return json from web api controller
body: <p>I have web api controller: </p>
  
  <pre><code>[HttpPost]
      public String UploadFile()
      {//do some logic
         String jsResult="{\"success\":\"false\", \"msg\":\"No file or user ID!\"}";
         return jsResult;
      }
  </code></pre>
  
  <p>Returned string to the client is like this:  "{\"success\":\"false\", \"msg\":\"No file or user ID!\"}"; </p>
  
  <p>I compose json string manually but client doesn't parse it(I guess because returned string is escaped with "\".
  What would be the proper way to return json string to the clinet from this controller method?</p>