working on U4-5927 - this extends the base event class to have EventMessages which event consumers can add to, the trick is that there is a factory for these EventMessages, in a web context, the factory is a request based factory so that during a request all instances of the EventMessages are the same instance. All services then accept an instance of IEventMessagesFactory which they can then use when raising events. We'll then use this to send messages to the UI. Not sure if i should make this a resolver yet or not. Still a WIP!!

src/Umbraco.Core/CoreBootManager.cs

@@ -7,6 +7,7 @@ using System.Web;
 using AutoMapper;
 using Umbraco.Core.Cache;
 using Umbraco.Core.Configuration;
+using Umbraco.Core.Events;
 using Umbraco.Core.Exceptions;
 using Umbraco.Core.IO;
 using Umbraco.Core.Logging;
@@ -164,7 +165,9 @@ namespace Umbraco.Core
                 new FileUnitOfWorkProvider(),
                 new PublishingStrategy(),
                 ApplicationCache,
-                ProfilingLogger.Logger);
+                ProfilingLogger.Logger,
+                //default transient factory
+                new TransientMessagesFactory());
         }
 
         /// <summary>