Question

When I submit form using button it works fine (renders PartialView in the menuload div):

<% using (Ajax.BeginForm("Menu", null, new AjaxOptions { UpdateTargetId = "menuload", HttpMethod = "POST", LoadingElementId = "status-waiting" }, new { @id = "menuFormControl", enctype = "multipart/form-data"}))
                   { %> 
<input id="menuFormControlsubmit" type="submit" value="submit" ) />
                 <%  } %> 

But I want to do it using javascript, to load page parts. I try this:

<% using (Ajax.BeginForm("Menu", null, new AjaxOptions { UpdateTargetId = "menuload", HttpMethod = "POST", LoadingElementId = "status-waiting" }, new { @id = "menuFormControl", enctype = "multipart/form-data"})){  } %>  

                   <script language="javascript" type="text/javascript">
                       $("#menuFormControl").submit();                       
                    </script>

But it renders my PartialView on a whole page.
The code of the controller:

public ActionResult Menu()
        {
            return PartialView("~/Views/Shared/MenuUserControl.ascx");
        }

Answer 1

When you call

$("#menuFormControl").submit();

you are making the form be POSTed just like it would if you had used a traditional form (instead of an AJAX form). You will have to post the content of the form to the server using AJAX and insert the response.
Try something like

 $.ajax({
  type: 'POST',
  url: '<%= Url.Action("Menu", "MyMenuController") %>',
  data: $("#menuFormControl").serialize(),
  success: function(){ $("#menuFormControl").html(data); /* This will insert the HTML returned from the server */ }
});