<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"  assembly="Testing_Console" namespace="Testing_Console">
   <class name="Testing_Console.Project, Testing_Console" table="projects">
      <id name="Id" column="projects_id" type="Int32">
         <generator class="identity" />
      </id>
      
      <property name="Name" column="name" type="String" length="50" not-null="true" />
   </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"  assembly="Testing_Console" namespace="Testing_Console">
   <class name="Testing_Console.MixDesign, Testing_Console" table="mix_designs">
      <id name="Id" column="mix_designs_id" type="Int32">
         <generator class="identity" />
      </id>
      <property name="ProjectId" column="projects_id" not-null="false" type="Int32"/>
      <property name="Name" column="name" type="String" length="50"/>
      <property name="SpecifiedStrength" column="specified_strength" type="Int32"/>
      <many-to-one name="ProjectId" column="projects_id" foreign-key="FK_mix_designs_projects" class="Project" />
   </class>
</hibernate-mapping>

            Configuration cfg = new Configuration();
            cfg.AddAssembly("Testing_Console");

            ISessionFactory factory = cfg.BuildSessionFactory();
            ISession session = factory.OpenSession();
            ITransaction transaction = session.BeginTransaction();

            MixDesign mix = new MixDesign();
            mix.Name = "C4000";
            mix.SpecifiedStrength = 4000;

            session.Save(mix);
            transaction.Commit();
            session.Close();

      StackTrace   "   at NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(Type theClass) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionFactoryImpl.cs:line 608\r\n   at NHibernate.Impl.SessionImpl.GetClassPersister(Type theClass) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 3629\r\n   at NHibernate.Impl.SessionImpl.GetEntityPersister(Object obj) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 3637\r\n   at NHibernate.Impl.SessionImpl.IsUnsaved(Object obj, Boolean earlyInsert, Object self) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 1171\r\n   at NHibernate.Impl.SessionImpl.NullifyTransientReferences(Object value, IType type, Boolean earlyInsert, Object self) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 1102\r\n   at NHibernate.Impl.SessionImpl.NullifyTransientReferences(Object[] values, IType[] types, Boolean earlyInsert, Object self) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 1081\r\n   at NHibernate.Impl.SessionImpl.DoSave(Object theObj, EntityKey key, IEntityPersister persister, Boolean replicate, Boolean useIdentityColumn, CascadingAction cascadeAction, Object anything) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 953\r\n   at NHibernate.Impl.SessionImpl.DoSave(Object obj, Object id, IEntityPersister persister, Boolean useIdentityColumn, CascadingAction cascadeAction, Object anything) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 872\r\n   at NHibernate.Impl.SessionImpl.SaveWithGeneratedIdentifier(Object obj, CascadingAction action, Object anything) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 767\r\n   at NHibernate.Impl.SessionImpl.Save(Object obj) in D:\\Program Files\\NHibernate\\src\\src\\NHibernate\\Impl\\SessionImpl.cs:line 708\r\n   at Testing_Console.Program.Main(String[] args) in D:\\Projects\\Testing and Experimental\\Testing-Console\\Testing-Console\\Program.cs:line 24\r\n   at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)\r\n   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)\r\n   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()\r\n   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)\r\n   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)\r\n   at System.Threading.ThreadHelper.ThreadStart()"   string

    public class MixDesign
    {
        public MixDesign()
        {

        }

        private int _id;

        public virtual int Id
        {
            get { return _id; }
            set { _id = value; }
        }

        private Project _project;

        public virtual Project Project
        {
            get { return _project; }
            set { _project = value; }
        }   

        private String _name;

        public virtual String Name
        {
            get { return _name; }
            set { _name = value; }
        }

        private Plant _plant;

        public virtual Plant Plant
        {
            get { return _plant; }
            set { _plant = value; }
        }

        private int _specifiedStrength;

        public virtual int SpecifiedStrength
        {
            get { return _specifiedStrength; }
            set { _specifiedStrength = value; }
        }
    }

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"  assembly="Testing_Console" namespace="Testing_Console">
   <class name="Testing_Console.MixDesign, Testing_Console" table="mix_designs">
      <id name="Id" column="mix_designs_id" type="Int32">
         <generator class="identity" />
      </id>
      <property name="Name" column="name" type="String" length="50"/>
      <property name="PlantId" column="plants_id" type="Int32" />
      <property name="SpecifiedStrength" column="specified_strength" type="Int32"/>
      <many-to-one name="Project" column="projects_id" foreign-key="FK_mix_designs_projects" class="Project" />
   </class>
</hibernate-mapping>