i have a problem with ajax.beginform, maybe someone can help.

    @using (Ajax.BeginForm("action", "controller", test, new AjaxOptions()
{
    InsertionMode = InsertionMode.Replace,
    UpdateTargetId = "formContent",
    OnSuccess = "formSuccess",
    OnBegin = "showLoader",
}, new { id="test123" }))

where test is object declared in viewmodel robot. action accepts viewmodel robot. every values from form is ok, but test is always null, but js function send array of numbers. Can someone tell me what im doing wrong?