title: Using Virtual on properties of a model
body: <p>I'm following a tutorial series about MVC4 on PluralSight and the presenter sets all of the properties of all of his models as virtual.  I haven't seen others do this and I was wondering if it is the right way to create models.  And further, what is the reason to use the virtual keyword.</p>
  
  <p>for example:</p>
  
  <pre><code>public class Video
  {
      public virtual int Id { get; set; }
      public virtual string Title { get; set; }
      public virtual int Length { get; set; }
  }
  </code></pre>