Selenium C# CssSelector using

Question

I'm trying to get element inside other element, but this element is not child.

Example code:

<form action="/Contact/SendContactForm" id="TopContactForm" method="post">
    <div id="contactform" name="contactform">
        <div id="contactformcontainter" class="clearfix">
            <input id="SenderName" name="SenderName" type="text" value="">
        </div>
    </div>
</form>

How can i simply get SenderName inside TopContactForm? I'm asking because there is two contact forms with same input id's and name's.