C# mvc2 nhibernate problem

Question

I've got the following mapping in my application. The mapping is generated, by a custom tool. Other mappings generated work ok, but this one is giving me a strange error which I don't understand.

This is the mapping;

<?xml version="1.0" encoding="utf-8"?>
<!--Generated by NHibernate.Mapping.Attributes on 2010-10-29 08:39:48Z.-->
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="Plugin.Twitter.Business.Entities.Tweet, Plugin.Twitter" table="PluginTwitter_Tweet">
    <id name="Id" column="Id">
      <generator class="guid" />
    </id>
    <property name="TweetMessage" />
    <property name="TweetDate" />
    <property name="TweetId" />
  </class>
</hibernate-mapping>

This is the error which i'm getting in the browser when i trying to open the website containing the mapping file;

The stacktrace with it is as below;

[InvalidOperationException: Could not find the dialect in the configuration]
   NHibernate.Dialect.Dialect.GetDialect(IDictionary 2 props) +204
   NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) +155

[MappingException: Could not compile the mapping document: Plugin.Twitter.Business.Entities.Hbm.Tweet.hbm.xml]
   NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) +534
   NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name) +378
   NHibernate.Cfg.Configuration.AddResource(String path, Assembly assembly) +419
   NHibernate.Cfg.Configuration.AddAssembly(Assembly assembly) +355
   NHibernate.Cfg.Configuration.AddAssembly(String assemblyName) +291
   CMS.ResourceAccess.DataAccessLogic.SessionManagement.SessionManager..ctor() in C:\Projects\Website\Website.ResourceAccess\DataAccessLogic\SessionManagement\SessionManager.cs:73
   Website.ResourceAccess.DataAccessLogic.SessionManagement.NestedSessionManager..cctor() in C:\Projects\Website\Website.ResourceAccess\DataAccessLogic\SessionManagement\SessionManager.cs:90

[TypeInitializationException: The type initializer for 'NestedSessionManager' threw an exception.]
   Website.ResourceAccess.DataAccessLogic.SessionManagement.SessionManager.get_Instance() in C:\Projects\Website\Website.ResourceAccess\DataAccessLogic\SessionManagement\SessionManager.cs:39
   CMS.ResourceAccess.DataAccessLogic.SessionManagement.SessionManager.get_SessionFactory() in C:\Projects\Website\Website.ResourceAccess\DataAccessLogic\SessionManagement\SessionManager.cs:23
   Website.Backend.MvcApplication.StartNHibernateSession() in C:\Projects\Website\Website.Web\Global.asax.cs:82
   Website.Backend.MvcApplication.Application_Start() in C:\Projects\Website\Website.Web\Global.asax.cs:47

[HttpException (0x80004005): The type initializer for 'NestedSessionManager' threw an exception.]
   System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +3988565
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +191
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +325
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +407
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +375

[HttpException (0x80004005): The type initializer for 'NestedSessionManager' threw an exception.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +11529072
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +141
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +4784373

I think the import thing to notice is that the exception i'm getting is an mapping exception as shown with this rule;

MappingException: Could not compile the mapping document: Plugin.Twitter.Business.Entities.Hbm.Tweet.hbm.xml]

I don't understand how and why though so I hope someone can tell me what the error means and how I can fix this issue. I've got the mapping marked as embedded resource.

UPDATE: We're using the following hibernate.cfg.xml file in the application.

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns='urn:nhibernate-configuration-2.2'>
  <session-factory>
    <property name="show_sql">true</property>
    <property name="dialect">NHibernate.Dialect.MsSql2008Dialect</property>
    <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
    <property name="connection.connection_string_name">NHibernate</property>
    <property name="current_session_context_class">managed_web</property>
    <property name='proxyfactory.factory_class'>NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu</property>
    <!--Needed for NH Profiler-->
    <property name="generate_statistics">false</property>
  </session-factory>
</hibernate-configuration>

Answer 1

This has little to do with your mapping.

It says: "Could not find the dialect in the configuration", so chances are big, you are not specifying a dialect in your configuration...

EDIT: Mappings work fine without a dialect as long as their PK generation is "native" or "sequence". This mapping is using "guid" wich requires a dialect.

But, you should always set the dialect property to get correct defaults for other configuration properties (without having to specify them manually)...