1 files changed, 65 insertions, 0 deletions
diff --git a/src/System.Web.Mvc/SingleServiceResolver.cs b/src/System.Web.Mvc/SingleServiceResolver.cs
new file mode 100644
index 00000000..b1f5c344
--- /dev/null
+++ b/src/System.Web.Mvc/SingleServiceResolver.cs
@@ -0,0 +1,65 @@
+using System.Globalization;
+using System.Web.Mvc.Properties;
+
+namespace System.Web.Mvc
+{
+    internal class SingleServiceResolver<TService> : IResolver<TService>
+        where TService : class
+    {
+        private TService _currentValueFromResolver;
+        private Func<TService> _currentValueThunk;
+        private TService _defaultValue;
+        private Func<IDependencyResolver> _resolverThunk;
+        private string _callerMethodName;
+
+        public SingleServiceResolver(Func<TService> currentValueThunk, TService defaultValue, string callerMethodName)
+        {
+            if (currentValueThunk == null)
+            {
+                throw new ArgumentNullException("currentValueThunk");
+            }
+            if (defaultValue == null)
+            {
+                throw new ArgumentNullException("defaultValue");
+            }
+
+            _resolverThunk = () => DependencyResolver.Current;
+            _currentValueThunk = currentValueThunk;
+            _defaultValue = defaultValue;
+            _callerMethodName = callerMethodName;
+        }
+
+        internal SingleServiceResolver(Func<TService> staticAccessor, TService defaultValue, IDependencyResolver resolver, string callerMethodName)
+            : this(staticAccessor, defaultValue, callerMethodName)
+        {
+            if (resolver != null)
+            {
+                _resolverThunk = () => resolver;
+            }
+        }
+
+        public TService Current
+        {
+            get
+            {
+                if (_resolverThunk != null)
+                {
+                    lock (_currentValueThunk)
+                    {
+                        if (_resolverThunk != null)
+                        {
+                            _currentValueFromResolver = _resolverThunk().GetService<TService>();
+                            _resolverThunk = null;
+
+                            if (_currentValueFromResolver != null && _currentValueThunk() != null)
+                            {
+                                throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture, MvcResources.SingleServiceResolver_CannotRegisterTwoInstances, typeof(TService).Name.ToString(), _callerMethodName));
+                            }
+                        }
+                    }
+                }
+                return _currentValueFromResolver ?? _currentValueThunk() ?? _defaultValue;
+            }
+        }
+    }
+}