nhibernate, could not resolve property

Question

I have a problem with NHibenate. When I run queryover, I get an error "could not resolve property: User.Name of: MegaOnlineChat.Core.Entities.Message".What am I doing wrong?

Entity objects

public class EntityObject<TId>
    {
        public virtual Int32 Id { get; set; }
    }
public class User:EntityObject<Int32>
    {
        public virtual String Name { get; set; }
        public virtual String Password { get; set; }
        public virtual Boolean Admin { get; set; }
        public virtual IList<Message> Messages { get; set; }
    }
public class Message:EntityObject<Int32>
    {
        public virtual String Text { get; set; }
        public virtual User User { get; set; }
        public virtual DateTime Date{ get; set; }
    }

Mapping

public class UserMapping:ClassMap<User>
{
    public UserMapping()
    {
        Table("Users");
        Id(m => m.Id).GeneratedBy.Native();
        Map(m => m.Name).Unique().Not.Nullable();
        Map(m => m.Admin).Not.Nullable();
        Map(m => m.Password).Not.Nullable();

        HasMany(m => m.Messages).KeyColumn("User_id");
    }
}
public class MessageMapping:ClassMap<Message>
{
    public MessageMapping()
    {
        Table("Messages");

        Id(m => m.Id).GeneratedBy.Native();

        Map(m => m.Text).Not.Nullable();
        Map(m => m.Date).Not.Nullable();

        References(m => m.User, "User_id").Not.Nullable();
    }
}

QueryOver

NHibernateSession.QueryOver<Message>().Where(x => x.User.Name == name).List<Message>().Last();

Martin Ernst · Accepted Answer · 2012-10-17 08:52:45Z

18

QueryOver is not the same as the Linq query provider. It would be easier to do:

NHibernateSession.Query<Message>().Where(x => x.User.Name == name).ToList();

But if you want to use QueryOver, you will need to explicitly join the relationships you want to navigate:

NHibernateSession.QueryOver<Message>()
    .JoinQueryOver(x => x.User) // navigate to the user on the relationship
    .Where(u => u.Name == name) // this restriction is on the User now
    .List();

you could also do this using an alias for user

answered Oct 17, 2012 at 8:52

Martin Ernst

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3 Comments

Mike Christensen Over a year ago

Is there a way to do this if you want to have additional .Where() clauses on Message?

Martin Ernst Over a year ago

If you're using the Linq provider, you can do something like: session.Query<Message>().Where(x => ...).Where(x => ..) etc.. - it will combine the Where's into 1 conjunction (AND) when it issues the query, if you're using QueryOver, you can use the .And(..) method

Mike Christensen Over a year ago

Ah, I figured it out. I was looking for .JoinAlias

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