Question

I’ve an entity with assigned string Id on NHibernate and I’ve a little problem when get an entity by Id.

Example…

Suppose that have a database record like this…

Id    Description
-------------------
AAA   MyDescription

now, if I use “Get” method using search id “aaa”…

MYENTITYTYPE entity = Session.Get<MYENTITYTYPE>("aaa")

return right entity but Id field (entity.Id) is “aaa”, while I wish it were equal to “AAA”.

In summary I would like that “Get” method return the id identical to the one stored in the database…with the same case.

Is possible? How can I do?

Answer 1

Interesting question. My guess is that it’s not possible, because the Id might exist before the DB call. Consider the following:

var foo = session.Load<Foo>("aaa"); //no DB call, foo is a proxy
Console.WriteLine(foo.Id); //Prints "aaa";
var bar = foo.Bar; //Forces loading
Console.WriteLine(foo.Id); //No matter what, the Id can't change at this point

This illustrates another reason why primary keys with meaning are usually a bad idea, especially if their input is not controlled.

Now, if instead of Get you use a query, you will get the right-cased Id:

//example with LINQ; you can use HQL, Criteria, etc
var foo = session.Query<Foo>().Single(x => x.Id == "aaa");

The drawback is that you will always go to the DB, even if the entity is already loaded.

Now, if you defined your entity as {Id, Code, Description}, where Id is a synthetic POID (I recommend Hilo or Guid) and Code is the existing string Id, you will avoid potential bugs caused by using Get instead of a query with the code.