public bool ChildLinksTo(N2.ContentItem item)
        {
            if (item == null)
                throw new ArgumentNullException("item", "item is null.");
            if(!item.IsPage)
                throw new InvalidOperationException("item is not a page");

            string url = item.GetSafeUrl().ToUri().AbsolutePath;

            // Destination URLs are forced to match the absolute path of the Safe URL for
            // internally Hyperlink items so there is no need to fetch the destination web page to
            // determine its safe url.

            return this.MapItems
                .Any(mapItem =>
                    mapItem.DestinationUrl == url
                 || mapItem.ChildLinksTo(item));
        }