Rename namespace from Umbraco.Core.Resolving to Umbraco.Core.ObjectResolution

src/Umbraco.Core/ObjectResolution/ResolverBase.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Threading;
+
+namespace Umbraco.Core.ObjectResolution
+{
+	/// <summary>
+	/// base class for resolvers which declare a singleton accessor
+	/// </summary>
+	/// <typeparam name="TResolver"></typeparam>
+	internal abstract class ResolverBase<TResolver> 
+		where TResolver : class
+	{
+		static TResolver _resolver;
+		
+		/// <summary>
+		/// The lock for the singleton
+		/// </summary>
+		/// <remarks>
+		/// Though resharper says this is in error, it is actually correct. We want a different lock object for each generic type.
+		/// See this for details: http://confluence.jetbrains.net/display/ReSharper/Static+field+in+generic+type
+		/// </remarks>
+		static readonly ReaderWriterLockSlim ResolversLock = new ReaderWriterLockSlim();
+
+		public static TResolver Current
+		{
+			get
+			{
+				using (new ReadLock(ResolversLock))
+				{
+					if (_resolver == null)
+						throw new InvalidOperationException("Current has not been initialized. You must initialize Current before trying to read it.");
+					return _resolver;
+				}
+			}
+
+			set
+			{
+				using (new WriteLock(ResolversLock))
+				{
+					if (value == null)
+						throw new ArgumentNullException("value");
+					if (_resolver != null)
+						throw new InvalidOperationException("Current has already been initialized. It is not possible to re-initialize Current once it has been initialized.");
+					_resolver = value;
+				}
+			}
+		}
+
+		/// <summary>
+		/// used in unit tests to reset current to null
+		/// </summary>
+		internal static void Reset()
+		{
+			_resolver = null;
+		}
+	}
+}