R – NHibernate query for object with child collection property

criteriahqlnhibernate

I need help with an nhibernate query. I would prefer to use Criteria API if possible, otherwise HQL is ok.

I have an Employee object with an Account object property, the Account has a collection of Entry objects, and each Entry has an Amount property.

I need a query that will return all employees who have an account where the sum of the Entry.Amount is less than zero.

Any ideas?

Best Answer

As shown here:

ICriteria.CreateCriteria(typeof(Customer))
.Add(Expression.Eq("Firstname", "Steve"))
.CreateCriteria("Orders")
.Add(Expression.Gt("OrderDate", new  Datetime.Now)))
.List<Customer>();

Related Solutions

How to delete child object in NHibernate

You are getting the first error because, when you remove the items from the collection, NHibernate's default mode of operation is to simply break the association. In the database, NHibernate tries to set the foreign key column on the child row to null. Since you do not allow nulls in that column, SQL Server raises the error. Clearing the collection will not necessarily delete the child object, but one way to do so is to set cascade=all-delete-orphan. This informs NHibernate that it should delete the newly orphaned rows instead of setting the foreign key column.

You are getting the second error because when you call SaveOrUpdate NHibernate first deletes all of the child objects. Then, because neither relationship is marked as inverse, NHibernate also tries to set the foreign key column in your child table to null. Since the rows have already been deleted, you receive the second error. You need to set inverse=true on one side of your relationship to fix this. This is usually done on the one (primary key or parent) side. If you do not do this, NHibernate will make the appropriate updates for each side of the relationship. Unfortunately, running two updates is not the appropriate thing to do.

You should always mark one side of your relationships as the inverse side. Depending on how you code, you may or may not need to use cascading. If you want to take advantage of one shot deletes as you are trying to do using Clear(), you need to define your cascade.

R – How to a write a Criteria query with multiple joins involved

You can use alias

var userList = _session
        .CreateCriteria(typeof(User), "u")
        .CreateAlias("u.Role", "r")
        .Add(Restrictions.Eq("r.ID", 3) )
        .CreateAlias("u.Customer", "c")
        .Add(Restrictions.Eq("c.ID", 1) )
        .List<User>();

Hope it helps

Best Answer

Related Solutions

How to delete child object in NHibernate

R – How to a write a Criteria query with multiple joins involved

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