Question

I have the following domain model

public interface IAppliedTo
{
    public Guid Id { get; set; }
}

public class Widget
{
    public DateTime DateCreated { get; set; }
    public Guid Id { get; set; }
    public ISet<IAppliedTo> AppliesTo { get; set; }
}


public class Master : IAppliedTo
{
    public Guid Id { get; set; }
}

Widget mapping has AppliesTo defined as:

<set name="AppliesTo" table="WidgetAppliesTo" lazy="true" >
    <key column="WidgetId"></key>
    <many-to-any  id-type="Guid" meta-type="int" >
      <meta-value  class="Master" value="1"/>

      <column name="ObjectType" />
      <column name="ObjectId" />

    </many-to-any>
  </set>

I am writing a query using QueryOver on Master, and I want to pull out the last CreatedDate for any Widget that applies to the Master.

Essentially I want something like:

            Master mast=null;
            Widget widg=null;
            var widgetQuery=QueryOver.Of<Widget>(()=>widg);

            var query = NHibernateSessionManager.Instance.GetSessionFrom()
                .QueryOver<Master>(() => mast)
                .Where(() => mast.Name == "Josh")
                .SelectList(l => 
                    l.SelectSubQuery(widgetQuery.Where(() => widg.AppliesTo.Contains(mast))
                        .Select(Projections.Max(() => widg.DateCreated))
                    )
                 );

If my AppliesTo was a specific type I’d know how to do this, but how can I tell nHibernate to use ObjectId. Essentially I am trying to get this query:

SELECT *,(SELECT MAX(DateCreated) 
          FROM Widget 
          INNER JOIN WidgetAppliesTo
            on Widget.Id=WidgetAppliesTo.ActivityId
            WHERE objectId=[master].Id)
FROM [Master]

Answer 1

So far the best I’ve managed to do is to use a Sql Projection to add this in.

    .Select(Projections.SqlProjection(
    "(select max(datecreated) from Widget wid
     inner join WidgetAppliesTo widTo on wid.Id=widTo.ActivityId and widTo.ObjectId=this_.Id)
 as lastTouchDate",
new string[]{"lastTouchDate"},
new NHibernate.Type.IType[]{NHibernateUtil.DateTime})
.WithAlias(() => jobDto.LastTouchDate));

While this works I’d love to see a non-hacked solution