Nhibernate Guid with PK MySQL

I've got a question. I use NHibernate with MySql. At my entities I use Id(PK) for my business-logic usage and Guid(for replication). So my BaseDomain:

 public class BaseDomain
 {
    public virtual int Id { get; set; }
    public virtual Guid Guid { get; set; }
    public class Properties
    {
        public const string Id = "Id";
        public const string Guid = "Guid";
    }
    public BaseDomain() { }
 }

My usage domain:

public class ActivityCategory : BaseDomain
{
    public ActivityCategory() { }
    public virtual string Name { get; set; }
    public new class Properties
    {
        public const string Id = "Id";
        public const string Guid = "Guid";
        public const string Name = "Name";
        private Properties() { }
    }
}

Mapping:

 <class name="ActivityCategory, Clients.Core" table='Activity_category'>
   <id name="Id" unsaved-value="0" type="int">
      <column name="Id" not-null="true"/>
      <generator class="native"/>
   </id>
   <property name="Guid"/>
   <property name="Name"/>
 </class>

But when I insert my entity:

[Test]
    public void Test()
    {
        ActivityCategory ac = new ActivityCategory();
        ac.Name = "Test";
        using (var repo = new Repository<ActivityCategory>())
            repo.Save(ac);
    }

I always get '00000000-0000-0000-0000-000000000000' at my Guid field. What should I do for generate right Guid. May be mapping?

Thanks a lot!

From a NHibernate perspective, you should either set the guid in C# or tell NHibernate that it is generated by the database.

In the former case, set the guid property in the constructor.

public class BaseDomain
{
    public BaseDomain()
    {
        Guid = Guid.NewGuid();
    }
}

You map a property whose value is generated in the database like this. Depending on how the value is generated, you may also need to exclude the property from insert statements.

<class name="ActivityCategory, Clients.Core" table="Activity_category">
    <id name="Id" not-null="true" >
        <generator class="native" />
    </id>
    <property name="Guid" generated="insert" insert="false" update="false" />
    <property name="Name" />
</class>