nhibernate weird DuplicateMappingException

I have two classes:

namespace fm.web
{
  public class User
  {
    public static string default_username = "guest";
    public static string default_password = "guest";

    private UserType usertype;

    public virtual int? Id { get; set; }
    public virtual string Username { get; set; }
    public virtual string Password { get; set; }
    public virtual DateTime Datecreated { get; set; }
    public virtual string Firstname { get; set; }
    public virtual string Lastname { get; set; }
    public virtual string Em开发者_如何学Cail { get; set; }
    public virtual UserType Usertype
    {
      get { return usertype; }
      set { usertype = value; }
    }    
  }
}

namespace fm.web
{
    public class UserType
    {
        public virtual int? Id { get; set; }
        public virtual string Title { get; set; }
    }
}

Here are the mapping files

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   namespace="fm.web"
                   assembly="fm.web">
  <class name="User" table="[user]">
    <id name="Id">
      <column name="id" />
      <generator class="native" />
    </id>
    <property name="Username" />
    <property name="Password" />
    <property name="Datecreated" />
    <many-to-one name="Usertype"
                 class="UserType"
                 column="[type]"
                 cascade="all"
                 lazy="false"
                 />
    <property name="Firstname" />
    <property name="Lastname" />
    <property name="Email" />
  </class>
</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   namespace="fm.web"
                   assembly="fm.web">
  <class name="UserType" table="[user_type]">
    <id name="Id">
      <column name="id" />
      <generator class="native" />
    </id>
    <property name="Title" />
  </class>

</hibernate-mapping>

I'm getting an exception: DuplicateMappingException

Could not compile the mapping document: fm.web.data.User.hbm.xml

Duplicate class/entity mapping User

Is nhibernate always this hard? Maybe I need a different framework.

I really think the mappings are fine which leads me to believe that the configuration setup is not quite right.

Please can you check that BuildSessionFactory is only called once on application start up. Also please check that you are not including the mapping files twice as this will also throw this type of error.

Please post your configuration code.

You are correct in thinking that NHibernate is difficult to grasp for new comers espically the session management and mappings. Once you have grasped this then things get easier and are well worth the effort.