Could not compile the mapping document nhibernate

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C#

NHibernate

mapping

It could not compile the mapping xml documents and i dont know why

this is my cfg file

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
  <!-- an ISessionFactory instance -->
  <session-factory>
    <!-- properties -->
    <property name="connection.provider">
      NHibernate.Connection.DriverConnectionProvider
    </property>
    <property name="connection.driver_class">
      NHibernate.Driver.MySqlDataDriver
    </property>
    <property name="connection.connection_string">
      Server=127.0.0.1;Database=projekt;User ID=root;Password=pass;
    </property>
    <property name="dialect">
      NHibernate.Dialect.MySQL5Dialect
    </property>
    <!-- mapping files -->
    <mapping resource="DBprojekt.mappings.Predajna.hbm.xml" assembly="DBprojekt" />
    <mapping resource="DBprojekt.mappings.Switch.hbm.xml" assembly="DBprojekt" />
    <mapping resource="DBprojekt.mappings.Server.hbm.xml" assembly="DBprojekt" />
    <mapping resource="DBprojekt.mappings.Typkamery.hbm.xml" assembly="DBprojekt" />
    <mapping resource="DBprojekt.mappings.Kamera.hbm.xml" assembly="DBprojekt" />
    <mapping resource="DBprojekt.mappings.Port.hbm.xml" assembly="DBprojekt" />
  </session-factory>
</hibernate-configuration>

this is .hbm.xml file

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="DBprojekt.classtable.Switch, DBprojekt" table="switch" lazy="true" >
    <id name="Id" column="id" type="int">
      <generator class="native"></generator>
    </id>
    <property name="Ip">
      <column name="ip" sql-type="char(20)" not-null="true" />
    </property>
    <many-to-one insert="false" update="false" lazy="false" name="Predajnaid">
      <column name="predajnaid" sql-type="int(11)" not-null="false" />
    </many-to-one>
    <property name="Predajnaid">
      <column name="predajnaid" sql-type="int(11)" not-null="false" />
    </property>
    <bag name="Ports" inverse="true" cascade="none">
      <key column="" />
      <one-to-many class="Port" />
    </bag>
    <bag name="Servers" inverse="true" cascade="none">
      <key column="" />
      <one-to-many class="Server" />
    </bag>
  </class>
</hibernate-mapping>

and class

using System;
using System.Text;
using System.Collections.Generic;


namespace DBprojekt.classtable
{

    public class Switch
    {
        public Switch()
        {
            Ports = new List<Port>();
            Servers = new List<Server>();
        }
        public virtual int Id { get; set; }
        public virtual Predajna Predajna { get; set; }
        public virtual string Ip { get; set; }
        public virtual IList<Port> Ports { get; set; }
        public virtual IList<Server> Servers { get; set; }
    }
}