title: Form returns null viewmodel to the Action
body: <p>I have a view model that contains following codes:</p>
  
  <pre><code>public IEnumerable&lt;MvcInternetShop.Models.DomainModels.Group&gt; Groups { get; set; }
  public MvcInternetShop.Models.DomainModels.Group Group { get; set; }
  </code></pre>
  
  <p>and I have an action for add a group:</p>
  
  <pre><code>public ActionResult AddGroup(Group model)
      {
          if (ModelState.IsValid)
          {
              if (gr.Add(model)) // gr is a GroupRepository for CRUD.
                  return JavaScript("notif({type: 'info',msg: 'Your Group Registerd.',width: 'all',height: 100,position: 'center'});");
              else
                  return JavaScript("notif({type: 'error',msg: 'Error.Try again!.',width: 'all',height: 100,position: 'center'});");
          }
          else
          {
              return JavaScript("notif({type: 'error',msg: '" + ModelState.GetErrors() + "',width: 'all',height: 100,position: 'center',modal:true});");//GetError() is a  myExtension method.
          }
      }
  </code></pre>
  
  <p>now in the view, I wanna post a group to the this action.
  I'm using a form for this:</p>
  
  <pre><code>@using (Ajax.BeginForm("AddGroup", "Admin", new AjaxOptions { HttpMethod="Post",Url="/Admin/AddGroup"}))
  {
      @Html.TextBoxFor(p=&gt;Model.Group.Name)//Model is a viewmodel that contains Group and Groups property.
      @Html.ValidationMessageFor(p =&gt; Model.Group.Name)  
      &lt;button type="submit" class="button"&gt;Add group&lt;/button&gt;}
  </code></pre>
  
  <p>but when I run that,the view returns a null model to the AddGroup action.
  in fact the name of textbox is not 'Name'. it is 'Group.Name'and because of that the action can not recognize the model properly.
  can anyone help me to resolve this problem?</p>