title: Remove duplicates from DropDownList from database MVC4
body: <p>I would like to take data from DB and add it to <code>DropDownList</code> in order to select an item in search panel, I want to remove duplicates items from the list (one author, many books). What should I do?</p>
  
  <pre><code>List&lt;string&gt; authorname = new List&lt;string&gt;();
  
  foreach (var item in DB.Books)
  {
      authorname.Add(item.BookDetails.authorname.ToString());
  }
  
  ViewData["AuthorName"] = new SelectList(authorname);
  </code></pre>