<p>It looks like the List within DependencyResolverTracker.AddResolverKey is used in a way which is possibly not be thread-safe.</p> <p>&nbsp;</p> <p>This caused us many IndexOutOfRangeExceptions randomly after an application pool recycle. Simply recycling the application pool again resolved the issue.</p> <p>&nbsp;</p> <p>Details of the stack are</p> <p>&nbsp;</p> <p>Exception is: IndexOutOfRangeException - Index was outside the bounds of the array. &amp;#xD;&amp;#xA;-----------------------------------------------&amp;#xD;&amp;#xA; At the time of the exception, the container was:&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA; Resolving Fred.Services.Person.ViewListing,ServiceHost (mapped from Fred.Services.Person.IViewListing, ServiceHost)&amp;#xD;&amp;#xA; ----&amp;gt; System.IndexOutOfRangeException: Index was outside the bounds of the array.&amp;#xA; at System.Collections.Generic.List`1.Add(T item)&amp;#xD;&amp;#xA; at Microsoft.Practices.ObjectBuilder2.ConstructorSelectorPolicyBase`1.CreateSelectedConstructor(IBuilderContext context, IPolicyList resolverPolicyDestination, ConstructorInfo ctor) in e:\Builds\Unity\UnityTemp\Compile\Unity\Unity\Src\ObjectBuilder\Strategies\BuildPl...).&quot; time=&quot;2012-02-16T21:14:59.0249474Z&quot;&gt;</p> <p>&nbsp;</p> <p>&nbsp;</p> <p>See this discussion for further info on it.</p> <p>http://unity.codeplex.com/discussions/328841</p> <p>&nbsp;</p> <p>Thanks</p> <p>Rick</p>

Message:    Index was outside the bounds of the array.

Stack:  at System.Collections.Generic.List`1.Enumerator.MoveNext()at System.Linq.Enumerable.WhereListIterator`1.MoveNext()at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)at Microsoft.Practices.Unity.NamedTypesRegistry.RegisterType(Type t, String name)at Microsoft.Practices.Unity.UnityDefaultBehaviorExtension.OnRegisterInstance(Object sender, RegisterInstanceEventArgs e)at System.EventHandler`1.Invoke(Object sender, TEventArgs e)at Microsoft.Practices.Unity.UnityContainer.RegisterInstance(Type t, String name, Object instance, LifetimeManager lifetime)at Microsoft.Practices.Unity.UnityContainerExtensions.RegisterInstance[TInterface](IUnityContainer container, TInterface instance, LifetimeManager lifetimeManager)at MyApp.UnityContainerConfiguratorBase.c__DisplayClass1.b__0() in c:\Builds\1\MyApp\Sources\MyApp\UnityContainerConfiguratorBase.cs:line 15at Saon.IrishJobs.WebUI.EducationSeoHandler.Handle() in c:\Builds\1\MyApp\Sources\WebUI\Infrastructure\Handler\EducationSeoHandler.cs:line 73at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)