How do you associate a MultiSelectList with a list of checkboxes?

eg. I pass something like this to the model

  model.Groups = new MultiSelectList(k.Groups, "Id", "Name", selectedGroups)

How should I render it? This doesn't work

<% foreach (var item in Model.Groups.Items) { %>
  <input type="checkbox" name="groups" value="<%=item.Value%>" id="group<%=item.Value%>" checked="<%=item.Selected?"yes":"no"%>" />
  <label for="group<%=item.Value%>"><%=item.Text%></label>
<% } %>

Error CS1061: 'object' does not contain a definition for 'Value'...

Is there a HTML Helper method that I can use?

(Then, unless it is straightforward, how should I then get the selected values back on the Controller when the form is submitted?)