Querying the instances of a class.

hcfk · **Posted:** Thu Jul 05, 2007 2:02 pm

Is there a way of querying the class list for finding the instances of a specific class.

For example

lets say

class abstract animal
{
....
}

class dog:animal
{
...
}

class cat:animal
{
.....
}

i want to find in nhibernate context the classes implementing animal which should be

{dog,cat}

marcal · **Posted:** Thu Jul 05, 2007 3:06 pm

Code:

session.CreateCriteria( typeof( animal ) ).List();

or

Code:

session.CreateQuery( "from animal" ).List();

will return all dogs and cats (animals).

Code:

session.CreateCriteria( typeof( dog ) ).List();

or

Code:

session.CreateQuery( "from dog" ).List();

will return all dogs.

Of course, all this assumes the inheritance mappings are correctly structured. Was there something more specific you wanted to do?

hcfk · **Posted:** Thu Jul 05, 2007 3:14 pm

I want to list the class names, not the instances of the classes.

the specified query will return
{Dog1, Dog2, Cat1, Cat2}

thanks in advance

karlchu · **Posted:** Thu Jul 05, 2007 4:07 pm

Calling ISessionFactory.GetAllClassMetadata() will return an IDictionary. The keys of the IDictionary are all the Types that NHibernate is aware of. You can do something like this:

Code:

IDictionary dict = sessionFactory.GetAllClassMetadata();
foreach (Type type in dict.Keys) {
    if (type.IsSubclassOf(typeof(Animal))) {
        // do whatever
    }
}

hcfk · **Posted:** Fri Jul 06, 2007 2:29 pm

i think there should be another way to implement this since if the object traversal may be costly if the classes in the context is much.

karlchu · **Posted:** Fri Jul 06, 2007 2:56 pm

Let us know if you find another way. I, for one, would be interested. Thanks.

hcfk · **Posted:** Sat Jul 07, 2007 3:24 am

Karl thanks again,
i looked for other possible solutions. Also i looked for the solution you have decided, i found that the solution u provided is not so costly. Providing that if any other solution is there it should use much more deeper reflection.
thanks again.