post string to controller asp.net mvc
<pre><code>//its in ajax success
document.getElementById('koeff').innerHTML = elements.total;//type string
</code></pre>

<p>Posting form:</p>

<pre><code>@using (Html.BeginForm("Index", "Power", FormMethod.Post))
{
        &lt;p&gt;Sum:  &lt;span id="koeff" name="mult"&gt;&lt;/span&gt;&lt;/p&gt;
      //other code with submit button
}
</code></pre>

<p>Controller:</p>

<pre><code>public ActionResult Index(string mult)//  mult null why?
{
}
</code></pre>

<p>In controller mult always null, why?</p>