Web.PublishedCache - add XPathNavigatorIsNavigable to caches

src/Umbraco.Web/PublishedCache/ContextualPublishedCache.cs

@@ -201,6 +201,12 @@ namespace Umbraco.Web.PublishedCache
         /// <returns>The XPath navigator.</returns>
         public abstract XPathNavigator GetXPathNavigator(bool preview);
 
+        /// <summary>
+        /// Gets a value indicating whether <c>GetXPathNavigator</c> returns an <c>XPathNavigator</c>
+        /// and that navigator is a <c>NavigableNavigator</c>.
+        /// </summary>
+        public abstract bool XPathNavigatorIsNavigable { get; }
+
         /// <summary>
         /// Gets a value indicating whether the underlying non-contextual cache contains content.
         /// </summary>

src/Umbraco.Web/PublishedCache/ContextualPublishedCacheOfT.cs

@@ -132,6 +132,12 @@ namespace Umbraco.Web.PublishedCache
             return _cache.GetXPathNavigator(UmbracoContext, preview);
         }
 
+         /// <summary>
+        /// Gets a value indicating whether <c>GetXPathNavigator</c> returns an <c>XPathNavigator</c>
+        /// and that navigator is a <c>NavigableNavigator</c>.
+        /// </summary>
+        public override bool XPathNavigatorIsNavigable { get { return _cache.XPathNavigatorIsNavigable; } }
+
         /// <summary>
         /// Gets a value indicating whether the underlying non-contextual cache contains content.
         /// </summary>

src/Umbraco.Web/PublishedCache/IPublishedCache.cs

@@ -88,6 +88,12 @@ namespace Umbraco.Web.PublishedCache
         /// <remarks>The value of <paramref name="preview"/> overrides the context.</remarks>
         XPathNavigator GetXPathNavigator(UmbracoContext umbracoContext, bool preview);
 
+        /// <summary>
+        /// Gets a value indicating whether <c>GetXPathNavigator</c> returns an <c>XPathNavigator</c>
+        /// and that navigator is a <c>NavigableNavigator</c>.
+        /// </summary>
+        bool XPathNavigatorIsNavigable { get; }
+
         /// <summary>
         /// Gets a value indicating whether the cache contains published content.
         /// </summary>

src/Umbraco.Web/PublishedCache/XmlPublishedCache/PublishedContentCache.cs

@@ -320,6 +320,8 @@ namespace Umbraco.Web.PublishedCache.XmlPublishedCache
             return xml.CreateNavigator();
         }
 
+        public virtual bool XPathNavigatorIsNavigable { get { return false; } }
+
         #endregion
 
         #region Legacy Xml

src/Umbraco.Web/PublishedCache/XmlPublishedCache/PublishedMediaCache.cs

@@ -92,6 +92,8 @@ namespace Umbraco.Web.PublishedCache.XmlPublishedCache
             throw new NotImplementedException("PublishedMediaCache does not support XPath.");
         }
 
+        public bool XPathNavigatorIsNavigable { get { return false; } }
+
         public virtual bool HasContent(UmbracoContext context, bool preview) { throw new NotImplementedException(); }
 
         private ExamineManager GetExamineManagerSafe()