Question

I’m mapping my database tables using NHibernate with NHibernate.Mapping.Attributes library and I got stuck to get the Filter attributes to work.

Suppose a class A that has a set of objects of class B. So, I have, the following:

[NHibernate.Mapping.Attributes.Set(0, Inverse = true, Lazy = NHibernate.Mapping.Attributes.CollectionLazy.False)]
[NHibernate.Mapping.Attributes.Key(1, Column = "ClassAId")]
[NHibernate.Mapping.Attributes.OneToMany(2, Class = "ClassB, Assembly")]

    public virtual ISet<ClassB> ClassBs { get; set; }

I want to create a filter on this collection to bring only class B objects that satisfy a given criteria, such as Status = 1.

How can I create such Filter?

Answer 1

The where parameter of the Set mapping should be able help you out. Per the documentation the where parameter:

where: (optional) specify an arbitrary
SQL WHERE condition to be used when
retrieving or removing the collection
(useful if the collection should
contain only a subset of the available
data)

So to filter on Status (assuming Status is a SQL column in the table mapped for ClassB – though this column does not have to be mapped in the NHibernate mapping).

[NHibernate.Mapping.Attributes.Set(0,...., Where = "Status = 1", .....)]
...
public virtual ISet<ClassB> ClassBs { get; set; }