Added singleton for managing ILookups collection, allows for adding/removing/inserting at runtime/startup

src/Umbraco.Web/Routing/DocumentRequest.cs

@@ -251,7 +251,8 @@ namespace Umbraco.Web.Routing
             // the first successful lookup, if any, will set this.Node, and may also set this.Template
             // some lookups may implement caching
             Trace.TraceInformation("{0}Begin lookup", tracePrefix);
-            _environment.Lookups.Any(lookup => lookup.LookupDocument(this));
+        	var lookups = _environment.RouteLookups.GetLookups();
+			lookups.Any(lookup => lookup.LookupDocument(this));
             Trace.TraceInformation("{0}End lookup, {1}", tracePrefix, (this.HasNode ? "a document was found" : "no document was found"));
 
             // fixme - not handling umbracoRedirect

src/Umbraco.Web/Routing/RouteLookups.cs

@@ -0,0 +1,105 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using Umbraco.Core;
+
+namespace Umbraco.Web.Routing
+{
+	/// <summary>
+	/// Represents a collection of ILookups used for routing that are registered in the application
+	/// </summary>
+	internal class RouteLookups
+	{
+		private static readonly List<ILookup> Lookups = new List<ILookup>();
+		private static readonly ReaderWriterLockSlim Lock = new ReaderWriterLockSlim();
+
+		/// <summary>
+		/// Singleton accessor
+		/// </summary>
+		public static RouteLookups Current { get; internal set; }
+
+		internal RouteLookups(IEnumerable<ILookup> lookups)
+		{
+			Lookups.AddRange(SortByWeight(lookups));
+		}
+
+		/// <summary>
+		/// Returns all of the lookups
+		/// </summary>
+		/// <returns></returns>
+		public IEnumerable<ILookup> GetLookups()
+		{
+			return Lookups;
+		} 
+
+		/// <summary>
+		/// Removes an ILookup based on the specified Type
+		/// </summary>
+		/// <typeparam name="T"></typeparam>
+		public void RemoveLookup<T>()
+			where T : ILookup
+		{
+			using (new WriteLock(Lock))
+			{
+				Lookups.Remove(Lookups.SingleOrDefault(x => x is T));	
+			}			
+		}
+
+		/// <summary>
+		/// Adds a new lookup to the end of the list
+		/// </summary>
+		/// <param name="lookup"></param>
+		public void AddLookup(ILookup lookup)
+		{			
+			if (CheckExists(lookup)) 
+				throw new InvalidOperationException("The lookup type " + lookup.GetType() + " already exists in the lookup collection");
+
+			using (new WriteLock(Lock))
+			{
+				Lookups.Add(lookup);
+			}			
+		}
+
+		/// <summary>
+		/// Inserts a lookup at the specified index
+		/// </summary>
+		/// <param name="index"></param>
+		/// <param name="lookup"></param>
+		public void InsertLookup(int index, ILookup lookup)
+		{
+			if (CheckExists(lookup))
+				throw new InvalidOperationException("The lookup type " + lookup.GetType() + " already exists in the lookup collection");
+			
+			using (new WriteLock(Lock))
+			{
+				Lookups.Insert(index, lookup);
+			}			
+		}
+
+		/// <summary>
+		/// checks if a lookup already exists by type
+		/// </summary>
+		/// <param name="lookup"></param>
+		/// <returns></returns>
+		private static bool CheckExists(ILookup lookup)
+		{
+			return Lookups.Any(x => x.GetType() == lookup.GetType());
+		}
+
+		/// <summary>
+		/// Sorts the ILookups in the list based on an attribute weight if one is specified
+		/// </summary>
+		/// <param name="lookups"></param>
+		/// <returns></returns>
+		private static IEnumerable<ILookup> SortByWeight(IEnumerable<ILookup> lookups)
+		{
+			return lookups.OrderBy(x =>
+				{
+					var attribute = x.GetType().GetCustomAttributes(true).OfType<LookupWeightAttribute>().SingleOrDefault();
+					return attribute == null ? LookupWeightAttribute.DefaultWeight : attribute.Weight;
+				}).ToList();
+		}
+
+	}
+}

src/Umbraco.Web/Routing/RoutingEnvironment.cs

@@ -11,25 +11,16 @@ namespace Umbraco.Web.Routing
     internal class RoutingEnvironment
     {
         public RoutingEnvironment(
-            IEnumerable<ILookup> lookups,
+            RouteLookups lookups,
             ILookupNotFound lookupNotFound,
             ContentStore contentStore)
         {
-            Lookups = SortByPartWeight(lookups);
+            RouteLookups = lookups;
             LookupNotFound = lookupNotFound;
             ContentStore = contentStore;
         }
 
-        private static IEnumerable<ILookup> SortByPartWeight(IEnumerable<ILookup> lookups)
-        {
-            return lookups.OrderBy(x =>
-                {
-                    var attribute = x.GetType().GetCustomAttributes(true).OfType<LookupWeightAttribute>().SingleOrDefault();
-                    return attribute == null ? LookupWeightAttribute.DefaultWeight : attribute.Weight;
-                }).ToList();
-        }
-
-    	public IEnumerable<ILookup> Lookups { get; private set; }
+		public RouteLookups RouteLookups { get; private set; }
 
     	public ILookupNotFound LookupNotFound { get; private set; }