nhibernatequeryovernhibernate-projections

NHibernate QueryOver, Projections and Aliases

I have an nhibernate issue where I am projecting the sql Coalesce function.

I am comparing two string properties having the same name, from two different entities. In the resulting sql, the same property from only the first entity is being compared thus:

var list = Projections.ProjectionList();
list.Add(
   Projections.SqlFunction("Coalesce",
    NHibernateUtil.String,
    Projections.Property<TranslatedText>(tt => tt.ItemText),
    Projections.Property<TextItem>(ti => ti.ItemText)));

var q = Session.QueryOver<TextItem>()
    .Left.JoinQueryOver(ti => ti.TranslatedItems);

Evaluating q results in this sql

coalesce(this_.ItemText, this_.ItemText)

the this_ in the RHS needs to be an aliased table

I can use Projections.Alias(Projections.Property<TranslatedText>(tt => tt.ItemText), "ttAlias") but am not sure how to map "ttAlias" in the JoinQueryOver.

I can create an alias there too, but can't see how to name it.

TranslatedText ttAlias = null;
...
JoinQueryOver(ti => ti.TranslatedItems, () => ttAlias)
Solution

  • Aliases are variables in QueryOver, like you showed in the JoinQueryOver call. Alias names (strings) should not be needed in QueryOver, they are for Criteria queries.

    To the problem itself: I can't test it right now, but I think this should work:

    Projections.Property(() => ttAlias.ItemText)