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nhibernatenhibernate-criteria

NHibernate: Combining result transformers?

I'm working with the criteria API, querying against a mapping file that I cannot really change. There is a root entity with many child entities joined to it and certain queries have required us to add 

criteria.SetResultTransformer(CriteriaSpecification.DistinctRootEntity);

in order to avoid getting duplicate entities when there are multiple SQL result-lines due to the joins. The problem is that now I also want to apply an alias-to-bean transformer, like so:

criteria.SetResultTransformer(Transformers.AliasToBean(typeof(MyDto)));

Using either one of these works great. However, I need to combine them: I want to load only the required columns into a DTO object, and also get only distinct root entities. How can I do this?

Solution

  • To load only required column into DTO you can use projection with DistinctEntityRootTransformer as follows

    ICriteria criteria = session.CreateCriteria(typeof(YourEntity));
criteria.SetProjection(
Projections.Distinct(Projections.ProjectionList()
    .Add(Projections.Alias(Projections.Property("Property"), "Property")));

criteria.SetResultTransformer(
new NHibernate.Transform.AliasToBeanResultTransformer(typeof(MyDto)));

IList list = criteria.List();