tracking NullReferenceExceptions in sitecore

Question

i'm trying to track a NullReferenceException that shows up on sitecore 6.5 at loading any webpage:

[NullReferenceException: Object reference not set to an instance of an object.]
   Sitecore.Diagnostics.Log.Error(String message, Exception exception, Type ownerType) +133
   Sitecore.Diagnostics.Log.Error(String message, Type ownerType) +45
   Sitecore.Configuration.Factory.LoadAutoIncludeFiles(ConfigPatcher patcher, String folder) +680
   Sitecore.Configuration.Factory.LoadAutoIncludeFiles(XmlNode element) +63
   Sitecore.Configuration.Factory.GetConfiguration() +347
   Sitecore.Diagnostics.LoggerFactory..cctor() +67

[TypeInitializationException: The type initializer for 'Sitecore.Diagnostics.LoggerFactory' threw an exception.]
   Sitecore.Diagnostics.LoggerFactory.GetLogger(Type type) +17
   Sitecore.Diagnostics.Log.Error(String message, Exception exception, Type ownerType) +93
   Sitecore.Diagnostics.Log.Error(String message, Type ownerType) +45
   Sitecore.Configuration.Factory.LoadAutoIncludeFiles(ConfigPatcher patcher, String folder) +680
   Sitecore.Configuration.Factory.LoadAutoIncludeFiles(XmlNode element) +63
   Sitecore.Configuration.Factory.GetConfiguration() +347
   Sitecore.Configuration.Factory.GetConfigNode(String xpath, Boolean assert) +82
   Sitecore.Configuration.Factory.GetConfigNode(String xpath) +29
   Sitecore.Resources.Media.UploadWatcher.InitializeIgnoreList() +114
   Sitecore.Resources.Media.UploadWatcher..cctor() +51

[TypeInitializationException: The type initializer for 'Sitecore.Resources.Media.UploadWatcher' threw an exception.]
   Sitecore.Resources.Media.UploadWatcher..ctor() +0

[TargetInvocationException: Exception has been thrown by the target of an invocation.]
   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +98
   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +241
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +69
   System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes) +1136
   System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes) +111
   System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture) +23
   System.Web.HttpRuntime.CreateNonPublicInstance(Type type, Object[] args) +60
   System.Web.HttpApplication.BuildIntegratedModuleCollection(List`1 moduleList) +231
   System.Web.HttpApplication.GetModuleCollection(IntPtr appContext) +1365
   Microsoft.Web.Infrastructure.DynamicModuleHelper.DynamicModuleReflectionUtil.GetIntegratedModuleCollection(HttpApplication target, IntPtr appContext) +33
   Microsoft.Web.Infrastructure.DynamicModuleHelper.CriticalStatics.Init(HttpApplication context) +179
   Microsoft.Web.Infrastructure.DynamicModuleHelper.IntegratedDynamicModule.Init(HttpApplication context) +6
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +517
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +194
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +339
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +253

[HttpException (0x80004005): Exception has been thrown by the target of an invocation.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9087676
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +97
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +256

the interesting characteristics that make this error hard to track are the following:

1) i get the following error in the sitecore log:

Exception: System.InvalidOperationException
Message: 'analytics' connection string is not defined
Source: Sitecore.Kernel
   at Sitecore.Diagnostics.Assert.IsNotNull(Object value, String message)
   at Sitecore.Diagnostics.Assert.ResultNotNull[T](T result, String message)
   at Sitecore.Analytics.Data.DataAccess.DataAdapters.DataAdapterManager.ConnectionStrings.get_AnalyticsSettings()
   at Sitecore.Analytics.Data.DataAccess.DataAdapters.DataAdapterManager.ConnectionStrings.get_Analytics()
   at Sitecore.Analytics.Data.DataAccess.DataAdapters.Sql.SqlServer.SqlServerDataAdapterProvider..ctor()

however analytics is very well disabled:

<setting name="Analytics.DisableDatabase" value="true" />
...
<setting name="Analytics.Enabled" value="false" />

2) the error goes away when i debug with visual studio, attach to IIS, and hit at least one breakpoint (if i don't hit any breakpoint, the error stays)

3) the error shows up again when i do a build, or touch web.config. Haven't tried rebuild, as that will delete important sitecore dlls from Website/bin

more info about my environment: visual studio 2010, IIS 7, sitecore 6.5, windows 7

how would you track this error?

Answer 1

Ok after half day of debugging and decompiling i found out the problem was the (internal) class Sitecore.Configuration.ConfigPatcher, it seems to choke with Sitecore.WebDav.[Debug/Release].config files that are used for xdt transformations of the Sitecore.WebDav.config file for the content delivery and content authoring environment.

For now, the workaround is rename these files (and disable xdt transformations)

However, this problem should affect any user of xdt transformations for non-web.config files (i'm using slow cheetah add-in)

Answer 2

Also you can get this error when you have empty configuration section in config file with patching, like this

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">

</configuration>