If you are using Ajax.BeginForm() with multiple submit buttons similar to this:

// View.aspx
<% using (Ajax.BeginForm("Action", "Controller", 
           new AjaxOptions { UpdateTargetId = "MyControl",  }))
{ %>
    <span id="MyControl">
       <% Html.RenderPartial("MyControl"); %>
    </span>
<% } %>

//MyControl.ascx
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %>
<input name="prev" type="submit" value="prev" />
<input name="next" type="submit" value="next" />
//...

Everything is submitted to the controller fine but the params for the submit button that was clicked are absent from the Request. In otherwords Request["next"] and Request["prev"] are always null.

I looked in to the JavaScript in Microsoft.MvcAjax.js and it looks like the function Sys_Mvc_MvcHelpers$_serializeForm completely skips over the inputs that are of type 'submit'.

This doesn't seem logical at all. How else can you find out what button has been clicked?

It looks like a bug to me. Is there any logical reason to skip these form parameters?