Get a list of a class by one of it's field?

igoro1975 · **Posted:** Sun Jul 23, 2006 2:04 am

Hi!

I am a new user of NHibernate. From the beginning I'd like understand the right principles of working with NHibernate.
So, maybe my question is a simple one but I have doubts...

Let's say I have a Product class and it has Category field.
How can I receive all products by a category?

Code:

public List<Product> GetByCategory(int categoryId)
{

}

Thank you.

anandbn · **Posted:** Mon Jul 24, 2006 4:22 am

Try:

Code:

Query q = session.createQuery("from Product p where p.category.categoryid= :categoryId");
q.

igoro1975 · **Posted:** Tue Jul 25, 2006 1:28 am

anandbn wrote:

Try:

Code:

Query q = session.createQuery("from Product p where p.category.categoryid= :categoryId");
q.

Thank you.
So, I must use HQL to get, for example, Products by a Category? Can't I do it with mapping in xml file and...?

anandbn · **Posted:** Tue Jul 25, 2006 2:17 am

You could use Filters(if I remember correct). You can enable and disbale them programmatically. Refer to Chapter 17 of the reference guide.

Additionally you can define the HQL query in the mapping XML file and use Session.createNamedQuery("name in mapping xml");. That way the HQL can be modified without modifiying Java code.

igoro1975 · **Posted:** Tue Jul 25, 2006 2:27 am

anandbn wrote:

You could use Filters(if I remember correct). You can enable and disbale them programmatically. Refer to Chapter 17 of the reference guide.

Additionally you can define the HQL query in the mapping XML file and use Session.createNamedQuery("name in mapping xml");. That way the HQL can be modified without modifiying Java code.

Thanks, I'll try...

rolandz · **Posted:** Tue Jul 25, 2006 3:39 am

igoro1975 wrote:

Let's say I have a Product class and it has Category field.
How can I receive all products by a category?

Code:

public List<Product> GetByCategory(int categoryId)
{

}

It is assumed that you have open session object.

Code:

return session.CreateCriteria(typeof(YourType))
  .Add(Expression.Eq("CategoryID", categoryId))
  .List();

igoro1975 · **Posted:** Tue Jul 25, 2006 4:09 am

rolandz wrote:

igoro1975 wrote:

Let's say I have a Product class and it has Category field.
How can I receive all products by a category?

Code:

public List<Product> GetByCategory(int categoryId)
{

}

It is assumed that you have open session object.

Code:

return session.CreateCriteria(typeof(YourType))
  .Add(Expression.Eq("CategoryID", categoryId))
  .List();

O, it looks more readable :)
Thank you.