title: How to set a field unique in Entity Framework 4.1 code first? No annotation attibrute?
body: <p>I've been looking for a way to set a field unique , but i' am surprised i can't find anything like annotation on the field. In most of the resource online one have to write <code>SQL</code> in an <a href="https://stackoverflow.com/questions/4413084/unique-constraint-in-entity-framework-code-first">initializer</a>. i was even hoping i could find something like</p>
  
  <pre><code>modelBuilder.Entity&lt;Profile&gt;().HasKey(p =&gt; p.RollNumber);
  </code></pre>
  
  <p>in which <code>HasKey</code> could be <code>HasUnique</code> or even <code>HasUniqueKey</code> </p>
  
  <p>Is it that am not searching with the proper keyword or that annotation feature is simply not available (to my surprise ).</p>