Get specific column with NHibernate Query

Question

I have an application using NHibernate and C# language. I have an model with some relations and I want to create a query to get only one value. I've tried something like this:

public long GetIdCompany(long number)
{
    return session.QueryOver<Report>()
                  .Where(x => x.Number == number)
                  .Select(x => x.Equipament.Company.Id)
                  .Take(1);
}

but I didn't work. I just want to take the IdCompany in the the model Report.Equipament.Company.Id. It could be in queryover, linq, hql, etc...

As a side, you could probably shorten this to .Where(x => x.Number == number).Single().[Id prop] — csharpnumpty
– csharpnumpty, Commented Jul 27, 2012 at 12:58

GSerjo · Accepted Answer · 2012-07-27 21:24:38Z

9

You should use JoinAlias, so your request will looks like

    public long GetIdCompany(long number)
    {
        Equipament equipamentAlias = null;
        return session.QueryOver<Report>()
                      .Where(x => x.Number == number)
                      .JoinAlias(x => x.Equipament, () => equipamentAlias)
                      .Select(x => equipamentAlias.Company.Id)
                      .SingleOrDefault<long>();
    }

Here is excellent introduction to QueryOver

answered Jul 27, 2012 at 21:24

GSerjo

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Community · Accepted Answer · 2017-05-23 10:30:36Z

8

HQL

return session.CreateQuery(
        "select e.Company.id from Report r " +
        "    inner join r.Equipament e " +
        "where r.Number = :number")
    .SetInt64("number", number)
    .UniqueResult<long>();

LINQ

return session.Query<Report>()
    .Where(x => x.Number == number)
    .Select(x => x.Equipament.Company.Id)
    .Single();

QueryOver

See GSerjo's answer.

edited May 23, 2017 at 10:30

CommunityBot

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answered Jul 27, 2012 at 13:11

Miroslav Popovic

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2 Comments

Miroslav Popovic Over a year ago

@GSerjo Thanks. Pointed to your answer.

Felipe Oriani Over a year ago

Thank you Miroslav, I liked your awser but I would like to use QueryOVer.

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