NHibernate QueryOver association does not contain item

Question

could someone help me to translate LINQ expression to Nhibernate QueryOver

from m in messages
where !m.Recipients.Any(rcpt => rcpt.IsDeleted && rcpt.User = user)

I tried this

var qry = Session.QueryOver<UserMessage>();
qry.Where(m => m.Recipients.Any(r => !r.IsDeleted && r.User == user));

but got

System.Exception : Unrecognised method call: System.Linq.Enumerable:Boolean Any[TSource](System.Collections.Generic.IEnumerable1[TSource], System.Func2[TSource,System.Boolean]

Answer 1

!m.Recipients.Any(...) translates to a "not exists" sub-query. You will need a couple of aliases to correlate the sub-query with the main query, and the sub-query will need to have a projection to make NHibernate happy.

Try something like this:

UserMessage messageAlias = null;
UserMessage recipientMessageAlias = null;

var subquery = QueryOver.Of<MessageRecipient>()
    .JoinAlias(x => x.Message, () => recipientMessageAlias)
    .Where(x => x.IsDeleted == true) // your criteria
    .Where(x => x.User.Id == userId)
    .Where(() => recipientMessageAlias.Id == messageAlias.Id) // correlated subquery
    .Select(x => x.Id); // projection

var query = session.QueryOver(() => messageAlias)
    .Where(Subqueries.WhereNotExists(subquery));

return query.List();

Answer 2

I managed to it this way:

UserMessage messageAlias = null;

var qry = Session.QueryOver<UserMessage>(() => messageAlias);

UserMessageRecipient recipientAlias = null;

var deletedbyUser = QueryOver.Of(() => recipientAlias)
  .Select(x => x.Id)
  .Where( () => recipientAlias.Message.Id == messageAlias.Id
    && (recipientAlias.Recipient == query.User && recipientAlias.IsDeleted))
                .DetachedCriteria;
qry.Where(Subqueries.NotExists(deletedbyUser));

Answer 3

Try to use the Linq version with session.Query<> instead of QueryOver

var qry = Session.Query<UserMessage>();
qry.Where(m => m.Recipients.Any(r => !r.IsDeleted && r.User == user));