title: Restrict Blocks in ContentArea
body: <p>I'm having a issue restricting what kind of Block to be inserted in a ContentArea. What I want is that the SliderBlock's ContentArea property can only have insertion of a SlideItemBlock.</p>
  
  <pre><code>[ContentType(...)]
  public class SlideItemBlock : BlockData
  {
      [Required]
      Display(Name = "Image")]
      public virtual string Image { get; set;}
  }
  
  [ContentType(...)]
  public class SliderBlock : BlockData
  {
      [Required]
      [Display(Name = "Slides")]
      public virtual ContentArea Slides { get; set; }
      //Should only accept insertion of SlideItemBlock
  }
  </code></pre>
  
  <p>Or is this the wrong way to achive what I'm trying to restrict for the editor to not drag and drop wrong block types?</p>
  
  <p>As of now, I can create a SliderBlock and insert a SlideItemBlocks in it. If I then insert the created SliderBlock in a new SliderBlock I get a forever and ever loop and It breaks the site. This is what I'm trying to control.</p>