PublishedContent - the big refactoring

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

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Runtime.CompilerServices;
+
+namespace Umbraco.Web.PublishedCache.XmlPublishedCache
+{
+    static class UmbracoContextCache
+    {
+        static readonly ConditionalWeakTable<UmbracoContext, ConcurrentDictionary<string, object>> Caches
+            = new ConditionalWeakTable<UmbracoContext, ConcurrentDictionary<string, object>>();
+
+        public static ConcurrentDictionary<string, object> Current
+        {
+            get
+            {
+                var umbracoContext = UmbracoContext.Current;
+
+                // will get or create a value
+                // a ConditionalWeakTable is thread-safe
+                // does not prevent the context from being disposed, and then the dictionary will be disposed too
+                return umbracoContext == null ? null : Caches.GetOrCreateValue(umbracoContext);
+            }
+        }
+    }
+}