NHibernate weird error

Question

I am learning NHibernate, but failed. I sense that the error messages are not accurate.

Please help .

error message is

The following types may not be used as proxies:
SecondSolution.Domain.Product: method get_Id should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method set_Id should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method get_Name should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method set_Name should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method get_Category should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method set_Category should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method get_Discontinued should be 'public/protected virtual' or 'protected internal virtual'
SecondSolution.Domain.Product: method set_Discontinued should be 'public/protected virtual' or 'protected internal virtual'
   at NHibernate.Cfg.Configuration.ValidateEntities() in c:\Users\oskar.berggren\Documents\Projects\nhibernate-core-3\src\NHibernate\Cfg\Configuration.cs:line
1052
   at NHibernate.Cfg.Configuration.Validate() in c:\Users\oskar.berggren\Documents\Projects\nhibernate-core-3\src\NHibernate\Cfg\Configuration.cs:line 959
   at NHibernate.Cfg.Configuration.BuildSessionFactory() in c:\Users\oskar.berggren\Documents\Projects\nhibernate-core-3\src\NHibernate\Cfg\Configuration.cs:li
ne 1251
   at SecondSolution.Program.Main(String[] args) in C:\vs_workspace\SecondSolution\SecondSolution\Program.cs:line 22
Press any key to continue . . .

Class file

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

namespace SecondSolution.Domain
{
    class Product
    {
        public Product()
        {
            this.Name = "John";
        }
        public Guid Id { get; set; }        
        public string Name { get; set; }        
        public string Category { get; set; }        
        public bool Discontinued { get; set; }
    }
}

mapping

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"                    
                   assembly="SecondSolution"                    
                   namespace="SecondSolution.Domain">
  <class name="Product">
    <id name="Id">
      <generator class="guid" />
    </id>
    <property name="Name" />
    <property name="Category" />
    <property name="Discontinued" />
  </class>
</hibernate-mapping>

config:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
  <session-factory>
    <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>
    <property name="dialect">NHibernate.Dialect.MsSqlCeDialect</property>
    <property name="connection.driver_class">NHibernate.Driver.SqlServerCeDriver</property>
    <property name="connection.connection_string">Data Source=FirstSample.sdf</property>
    <property name="show_sql">true</property>  
  </session-factory>
</hibernate-configuration>

main class

static void Main(string[] args)
        {
            try
            {
                Configuration cfg = new Configuration();
                cfg.Configure("Mappings/hibernate.cfg.xml");
                //cfg.Configure();

                cfg.AddAssembly(typeof(Product).Assembly);

                NHibernate.ISessionFactory m_SessionFactory = cfg.BuildSessionFactory();
                NHibernate.ISession session = m_SessionFactory.OpenSession();
                Product product = new Product();
                session.SaveOrUpdate(product);
            } catch (Exception e)
            {
                Console.WriteLine(e.Message);
                Console.WriteLine(e.StackTrace);
            }

        }

Answer 1

As the others say - you must make your properties virtual. But this is only needed if you want your entity to be able to lazy load, read up on it here http://nhforge.org/wikis/howtonh/lazy-loading-eager-loading.aspx

If you dont want lazy loading you can disable it

<class name="Product" Lazy="false">

Then you wont need virtual properties.

Answer 2

As the error message says, NHibernate requires that the entity class properties be marked as virtual:

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

namespace SecondSolution.Domain
{
    class Product
    {
        public Product()
        {
            this.Name = "John";
        }
        public virtual Guid Id { get; set; }        
        public virtual string Name { get; set; }        
        public virtual string Category { get; set; }        
        public virtual bool Discontinued { get; set; }
    }
}