title: string parameter null in controller action
body: <p>I'm trying to upload a file with ASP.NET MVC Partial view.</p>
  
  <pre><code>**Partial view:**
  
  @using (Html.BeginForm("FileUpload", "Item", FormMethod.Post, new { enctype = "multipart/form-data", id="frmUp" }))
  {
      &lt;input type="file" name="file" /&gt;
      &lt;input type="submit" value="Upload" /&gt;
  }
  </code></pre>
  
  <p><strong>Main Form:</strong></p>
  
  <pre><code>&lt;div id="uploadDiv" class="divSettings" align="left"&gt;        
      @Html.Partial("FileUpload")
  &lt;/div&gt;
  </code></pre>
  
  <p>In my main form i have the below code.</p>
  
  <pre><code>$("#frmUp").submit(function () {
      var serviceURL = '/Item/FileUpload/';
      var id = $("#selID").val();
      alert(id);
      $.ajax({
          type: "POST",
          url: serviceURL,
          data: { id: id },
          dataType: "json",
          success: successFunc,
          error: errorFunc
      });
  
      function successFunc(data, status) {        
      }
  
      function errorFunc() {
      }
  });
  </code></pre>
  
  <p><strong>Controller:</strong></p>
  
  <pre><code>[HttpPost]
  public ActionResult FileUpload(HttpPostedFileBase file, string id, FormCollection formCollection)
  {
      //here id parameter is null and i get the file parameter values
      return PartialView();
  }
  </code></pre>
  
  <p>In my controller id parameter is always null. whats the issue with the above code?</p>