问题
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?
回答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.
来源：https://stackoverflow.com/questions/10781147/nhibernate-get-string-id