NHibernate - The most concise way to select multiple columns using QueryOver

Question

With Linq you can easily do:

from c in session.Query<Site>()
       select new {c.SiteName, c.SiteId, 
                   c.Network, c.RegionLocation.City, 
                   c.RegionLocation.Region.RegionName};

Is there a way to do something like this with QueryOver ? It seems that you can do it with SelectList but that does not seem as clean as linq approach. Is there a cleaner way ?

Answer 1

No not as far as I know, its a bit more verbose then Linq. But isn't this cleanish?

session.QueryOver<Sites>()
        .SelectList(x => x
          .Select(p => p.Name)
          .Select(p => p.Lat)
          .Select(p => p.Lng)
        )
        .TransformUsing(Transformers.AliasToBean<MarkerDto>())  
        .List<MarkerDto>();  

public class MarkerDto  
{  
  public string Name { get; set; }  
  public decimal? Lat { get; set; }  
  public decimal? Lng { get; set; }  
} 

If your select list is shared across multiple queries you can attempt to stay dry by using a projectionBuilder eg

Func<QueryOverProjectionBuilder<MarkerDto>, 
    QueryOverProjectionBuilder<MarkerDto>> GetDtoList() {
    MarkerDto dto = null;
    return list => list
      .Select(w => w.Name).WithAlias(() => dto.Name)
      .Select(w => w.Lat).WithAlias(() => dto.Lat)
      .Select(w => w.Lng).WithAlias(() => dto.Lng);
}

and use like

Session.QueryOver<Sites>()  
    .SelectList(GetDtoList())  
    .TransformUsing(Transformers.AliasToBean<MarkerDto>())  
    .List<MarkerDto>();  

A little bit cleaner but more cumbersome creating a projectionBuilder , however why change from Linq if it works for you?

I should also mention that it is possible to create a transformer that transforms into an anonymous type, see this blog post , disclaimer mine!