title: validate a dropdownlist in asp.net mvc
body: <pre><code>//in controller
  ViewBag.Categories = categoryRepository.GetAllCategories().ToList();
  
  //in view
   @Html.DropDownList("Cat", new SelectList(ViewBag.Categories,"ID", "CategoryName"))
  </code></pre>
  
  <p>How can I make it so that by default it says "-Select Category-"</p>
  
  <p>And validate to check something is selected (client and on the model)</p>
  
  <p>Thanks</p>