title: Html.DropDownListFor() with custom parameter
body: <p>I want to add extension method in HTML helpers for generating select and options like this</p>
  
  <pre><code>&lt;select id="Country" name="Country"&gt;
  &lt;option data-domain="AN" value="1"&gt;Andorra&lt;/option&gt;
  &lt;option data-domain="UI" value="2"&gt;United Arab Emirates&lt;/option&gt;
  &lt;option data-domain="AF" value="3"&gt;Afghanistan&lt;/option&gt;
  </code></pre>
  
  <p>the options have a data-domain attribute, and I can use it like this</p>
  
  <pre><code>@Html.DropDownListFor(m =&gt; m.Country, Model.CountryList)
  </code></pre>
  
  <p>the <code>Model.CountryList</code> is an arrayh of Country valiables</p>
  
  <pre><code>class Country
  {
      public String Text { get; set; }
      public String Value { get; set; }
      public String Domain { get; set; }
  }
  </code></pre>
  
  <p>please can anyone give a solution </p>