title: SelectListItem with data-attributes
body: <p>Is there anyway to have a SelectList prepopulated on ViewModel with data-attributes ?</p>
  
  <p>I want to do </p>
  
  <pre><code>@Html.DropdownListFor(m=&gt; m.CityId, Model.Cities);
  </code></pre>
  
  <p>so it generates code like :</p>
  
  <pre><code>&lt;select id="City" class="location_city_input" name="City"&gt;
      &lt;option data-geo-lat="-32.522779" data-geo-lng="-55.765835" data-geo-zoom="6" /&gt;
      &lt;option data-geo-lat="-34.883611" data-geo-lng="-56.181944" data-geo-zoom="13" data-geo-name="Montevideo" data-child=".state1" value="1"&gt;Montevideo&lt;/option&gt;               
      &lt;option data-geo-lat="-34.816667" data-geo-lng="-55.95" data-geo-zoom="13" data-geo-name="Canelones, Ciudad de la Costa" data-child=".state41" value="41"&gt;Ciudad de la Costa&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>