title: EF 4.1 Code First - model updated with [Required] attributes
body: <p>My model previously was without any DataNotations, but I recently changed that, applying [Required] for some properties. As this happen, my migration code start to throw an exception, like:</p>
  
  <blockquote>
    <p>Unable to apply pending changes because automatic migration is
    disabled. To enable automatic migration, ensure that
    DbMigrationsConfiguration.AutomaticMigrationsEnabled is set to true.</p>
  </blockquote>
  
  <p>I assume that some explicit actions of migration have to be done. Please clarify.</p>
  
  <p><strong>EDIT</strong>: AutomaticMigrationsEnabled = true is not option for me, I'm interesting how to make it possible with some migration scripts.</p>