How to select chosen columns from two different entities into one DTO using NHibernate?
- by Pawel Krakowiak
I have two classes (just recreating the problem):
public class User
{
public virtual int Id { get; set; }
public virtual string FirstName { get; set; }
public virtual string LastName { get; set; }
public virtual IList<OrgUnitMembership> OrgUnitMemberships { get; set; }
}
public class OrgUnitMembership
{
public virtual int UserId { get; set; }
public virtual int OrgUnitId { get; set; }
public virtual DateTime JoinDate { get; set; }
public virtual DateTime LeaveDate { get; set; }
}
There's a Fluent NHibernate map for both, of course:
public class UserMapping : ClassMap<User>
{
public UserMapping()
{
Table("Users");
Id(e => e.Id).GeneratedBy.Identity();
Map(e => e.FirstName);
Map(e => e.LastName);
HasMany(x => x.OrgUnitMemberships)
.KeyColumn(TypeReflector<OrgUnitMembership>
.GetPropertyName(p => p.UserId))).ReadOnly().Inverse();
}
}
public class OrgUnitMembershipMapping : ClassMap<OrgUnitMembership>
{
public OrgUnitMembershipMapping()
{
Table("OrgUnitMembership");
CompositeId()
.KeyProperty(x=>x.UserId)
.KeyProperty(x=>x.OrgUnitId);
Map(x => x.JoinDate);
Map(x => x.LeaveDate);
References(oum => oum.OrgUnit)
.Column(TypeReflector<OrgUnitMembership>
.GetPropertyName(oum => oum.OrgUnitId)).ReadOnly();
References(oum => oum.User)
.Column(TypeReflector<OrgUnitMembership>
.GetPropertyName(oum => oum.UserId)).ReadOnly();
}
}
What I want to do is to retrieve some users based on criteria, but I would like to combine all columns from the Users table with some columns from the OrgUnitMemberships table, analogous to a SQL query:
select u.*, m.JoinDate, m.LeaveDate
from Users u inner join OrgUnitMemberships m on u.Id = m.UserId
where m.OrgUnitId = :ouid
I am totally lost, I tried many different options. Using a plain SQL query almost works, but because there are some nullable enums in the User class AliasToBean fails to transform, otherwise wrapping a SQL query would work like this:
return
Session
.CreateSQLQuery(sql)
.SetParameter("ouid", orgUnitId)
.SetResultTransformer(Transformers.AliasToBean<UserDTO>())
.List<UserDTO>()
I tried the code below as a test (a few different variants), but I'm not sure what I'm doing. It works partially, I get instances of UserDTO back, the properties coming from OrgUnitMembership (dates) are filled, but all properties from User are null:
User user = null;
OrgUnitMembership membership = null;
UserDTO dto = null;
var users = Session.QueryOver(() => user)
.SelectList(list => list
.Select(() => user.Id)
.Select(() => user.FirstName)
.Select(() => user.LastName))
.JoinAlias(u => u.OrgUnitMemberships, () => membership)
//.JoinQueryOver<OrgUnitMembership>(u => u.OrgUnitMemberships)
.SelectList(list => list
.Select(() => membership.JoinDate).WithAlias(() => dto.JoinDate)
.Select(() => membership.LeaveDate).WithAlias(() => dto.LeaveDate))
.TransformUsing(Transformers.AliasToBean<UserDTO>())
.List<UserDTO>();
