private static bool IsAttribute(PostNodeBase node, PostNodeBasicAttribute attribute)
 {
     var n = node as PostNode;
     if (n == null)
     {
         return false;
     }
     var a = n.Attribute as PostNodeAttribute;
     if (a == null)
     {
         return false;
     }
     return a.Attribute == attribute;
 }
 private ICollection<PostNodeBase> AddToResult(ICollection<PostNodeBase> result, PostNodeBase node)
 {
     result.Add(node);
     return result;
 }