using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using NHibernate.Mapping.Attributes;

namespace Hairless.Entities.Presentation
{
    [Class(Table = "Presentations")]
    public abstract class Presentation
    {
        private int id;

        [Id(Name = "Id", Column = "PresentationId")]
        [Generator(1, Class = "identity")]
        public virtual int Id
        {
            get { return id; }
            set { id = value; }
        }

    }
}

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using NHibernate.Mapping.Attributes;

namespace Hairless.Entities.Presentation
{
    //[Class( Table = "BrandPresentation" )]
    [JoinedSubclass( Table = "BrandPresentation" , NameType = typeof(BrandPresentation), ExtendsType = typeof(Presentation))]
    public class BrandPresentation : Presentation
    {
        private String promotionImage;

        [Property]
        public String PromotionImage
        {
            get { return promotionImage; }
            set { promotionImage = value; }
        }


       
       

    }
}

System.TypeInitializationException: The type initializer for 'Hairless.Persistence.PersistenceHelper' threw an exception. ---> NHibernate.MappingException: (29,6): XML validation error: The element 'joined-subclass' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'property' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'urn:nhibernate-mapping-2.2:meta urn:nhibernate-mapping-2.2:key'. ---> System.Xml.Schema.XmlSchemaValidationException: The element 'joined-subclass' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'property' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'urn:nhibernate-mapping-2.2:meta urn:nhibernate-mapping-2.2:key'.
   --- End of inner exception stack trace ---
   at NHibernate.Cfg.Configuration.LogAndThrow(MappingException me)
   at NHibernate.Cfg.Configuration.ValidationHandler(Object o, ValidationEventArgs args)
   at System.Xml.Schema.XmlSchemaValidator.SendValidationEvent(ValidationEventHandler eventHandler, Object sender, XmlSchemaValidationException e, XmlSeverityType severity)
   at System.Xml.Schema.XmlSchemaValidator.ElementValidationError(XmlQualifiedName name, ValidationState context, ValidationEventHandler eventHandler, Object sender, String sourceUri, Int32 lineNo, Int32 linePos, Boolean getParticles)
   at System.Xml.Schema.XsdValidator.ValidateChildElement()
   at System.Xml.Schema.XsdValidator.ValidateElement()
   at System.Xml.Schema.XsdValidator.Validate()
   at System.Xml.XmlValidatingReaderImpl.ProcessCoreReaderEvent()
   at System.Xml.XmlValidatingReaderImpl.Read()
   at System.Xml.XmlValidatingReader.Read()
   at System.Xml.XmlLoader.LoadNode(Boolean skipOverWhitespace)
   at System.Xml.XmlLoader.LoadDocSequence(XmlDocument parentDoc)
   at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace)
   at System.Xml.XmlDocument.Load(XmlReader reader)
   at NHibernate.Cfg.Configuration.LoadMappingDocument(XmlTextReader hbmReader, String name)
   at NHibernate.Cfg.Configuration.AddXmlReader(XmlTextReader hbmReader, String name)
   at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name)
   at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream)
   at Hairless.Persistence.PersistenceHelper..cctor() in D:\Boardstore\Hairless\Hairless\Persistence\PersistenceHelper.cs:line 33
   --- End of inner exception stack trace ---
   at Hairless.Persistence.PersistenceHelper.GetCurrentSession()
   at Hairless.Service1.HelloWorld() in D:\Boardstore\Hairless\Hairless\Service1.asmx.cs:line 47