Doing queries with NHibernate

Question

I'm new to NHibernate, so this is a basic question..

When fetching data from the database through an NHibernate session I've only done it using the Id this far, e.g. like this:

var customer = Session.Get<Customer>(customerId); 

But how do I fetch an object based on a property that isn't the Id? E.g. fetch a customer by search on the Name property. This could return 0-n answers, so I'm assuming I would get a list back?

Answer 1

Using HQL it would look something like:

session.CreateQuery("from Customer where Name=:name")
       .SetString("name", name)
       .List<Customer>();

Answer 2

You basically have two options here: HQL and the Criteria API. The Hibernate documentation is fantastic, so I strongly suggest you read it rather than having me post an unnecessarily verbose answer.

Answer 3

Another option - Linq2NHibernate which is getting more and more mature lately.

usage looks like this=>

var employees = Session.Linq<Employee>()
    .Single(employee=>employee.Name==name);

Linq extension method returns INHibernateQueryable interface which implements IQueryable.

Answer 4

There are many ways of querying NHibernate:

• HQL
• Criteria
• Query by example
• Query over criteria
• LINQ (2 different linq providers available)
• H-SQL
• SQL
• You can implement your own way of querying