从Entity Framework查询转换为NHibernate的问题

Question

I am attempting to teach myself NHibernate after working exclusively with Entity Framework for a few years now. I know how I would write the query, and I know how I would write the code with EF and lambda expressions, but translating that to NHibernate is stumping me.

The query would be written as:

SELECT fb.*
FROM foo f
INNER JOIN bar b ON f.fooid = b.fooid
INNER JOIN foobar fb ON b.barid = fb.barid
WHERE f.otherid = 1

Basically, I know a key of my start table ( foo ), and I want to return all of the matching rows in the 2nd joined table ( foobar ). In EF, I would write:

public IEnumerable<foobar> GetFooBarInfo(int intFooID)
{
    return db.foo.Include(f => f.bar)
                 .Include(fb => fb.bar.foobar)
                 .Where(f => f.otherentity.fooid == intFooID)
                 .Select(fb => fb.bar.foobar)
                 .ToList();
}

Now converting that to NHibernate is where I need help. I have tried a few things, none of which I've saved, but the latest version returns 1 row instead of 7 rows. It looks like it is returning the one row in foobar where barid = 1 instead of all barid values where fooid = 1 .

public IEnumerable<foobar> GetFooBarInfo(int intFooID)
{
    foo f = null;
    bar b = null;
    foobar fb = null;

    return db.QueryOver<foo>(() => f)
             .Where(fi => fi.otherentity.fooid == intFooID)
             .Inner.JoinQueryOver(ba => ba.bar, () => b)
             .Inner.JoinQueryOver(fbar => fbar.foobar, () => fb)
             .Select(Projections.ProjectionList()
                                .Add(Projections.Property(() => fb.barid))
                                .Add(Projections.Property(() => fb.barname))
                                .Add(Projections.Property(() => fb.bardescription))
                    )
             .TransformUsing(Transformers.AliasToBean<foobar>())
             .List<foobar>();
}

I also just realized that it isn't truly filling the projection/transform. barid is 0 and barname and bardescription are null - these obviously have values in the database.

Answer 1

I was attempting to join foo and bar on fooid , but bar had its own primary key foobarid . Once I turned on logging for NHibernate, I could see the generated query was incorrect . It was generating:

SELECT fb.*
FROM foo f
INNER JOIN bar b ON f.fooid = b.foobarid
INNER JOIN foobar fb ON b.barid = fb.barid
WHERE f.otherid = 1

So then I realized I needed to include the parent table for bar , which was baz in order to get the join right. But this meant I needed to make the map for baz include:

.HasMany(x => x.bar).KeyColumn("fooid")
.HasMany(x => x.foobar).KeyColumn("barid")

Then alter the QueryOver to include this additional table. This got the result count right, but still wasn't projecting into the object properly - everything was null until I added the string alias on each Projection.Property() :

public IEnumerable<foobar> GetFooBarInfo(int intFooID)
{
    foo f = null;
    bar b = null;
    baz bz = null;
    foobar fb = null;

    return db.QueryOver<foo>(() => f)
             .Where(fi => fi.otherentity.fooid == intFooID)
             .Inner.JoinQueryOver(bb => bb.baz, () => bz)
             .Inner.JoinQueryOver(ba => ba.bar, () => b)
             .Inner.JoinQueryOver(fbar => fbar.foobar, () => fb)
             .Select(Projections.ProjectionList()
                      .Add(Projections.Property(() => fb.barid), "barid")
                      .Add(Projections.Property(() => fb.barname), "barname")
                      .Add(Projections.Property(() => fb.bardescription), "bardescription")
             )
             .TransformUsing(Transformers.AliasToBean<foobar>())
             .List<foobar>();
}