A simple example, where a change on a dropdown list triggers an ajax form-submit to reload a datagrid:
<div id="pnlSearch">
<% using (Ajax.BeginForm("UserSearch", "Home", new AjaxOptions { UpdateTargetId = "pnlSearchResults" }, new { id="UserSearchForm" }))
{ %>
UserType: <%: Html.DropDownList("FilterUserType", Model.UserTypes, "--", new { onchange = "$('#UserSearchForm').trigger('submit');" })%>
<% } %>
</div>
The trigger('onsubmit') is the key thing: it calls the onsubmit function that MVC has grafted onto the form.
NB. The UserSearchResults controller returns a PartialView that renders a table using the supplied Model
<div id="pnlSearchResults">
<% Html.RenderPartial("UserSearchResults", Model); %>
</div>