title: ValidationResults on TryValidateObject is null
body: <p>I am trying to get my head around data annotations.</p>
  
  <p>Here's my class:</p>
  
  <pre><code>public class Video
  {
      [Required]
      public string Title {get; set; }
  
      public List&lt;ValidationResult&gt; ValidationResults { get; set; }
  
      public bool IsValid()
      {
          var context = new ValidationContext(this, null, null);
          return Validator.TryValidateObject(this, context, this.ValidationResults);
      }
  }
  </code></pre>
  
  <p>If I create an object of type Video without setting a Title, IsValid returns false (correct!), but the ValidationResults of the objects are null. Aren't they suppose to contain a ValidationResult with an error message saying that video is required or something?</p>