how to do autofocus in mvc3 razor view

Hi am trying to do autofocus in my view page.I tried the below coding but it focusing the label not Textbox

<div class="contact_form">
    <div class="contact_form1">
    @Html.LabelFor(model => model.Prefix)
    </div>
    @Html.TextBoxFor(model => model.Prefix, new { autofocus = "autofocus",
    @class = "name_form" })
    @Html.ValidationMessageFor(model => model.Prefix)
    </div>

any one please help me to get out of this problem