NHibernate + default getdate() column

Question

How do I configure NHibernate to create the db schema with a column like this:

create_dt datetime not null default getdate()

I have this in the mapping file:

<property name="create_dt" update="false" insert="false" generated="insert" not-null="true" />

Is there anyway I can inject the sql server specific default getdate(). The documentation for generated properties even mentions this is how you handle a create_date field. I'm just not sure how to make my db schema generate properly. Will I have to edit the create table scripts manually?

Similar question.

EDIT: I figured out I can always change the table schema like so:

<database-object>
    <create>ALTER TABLE Report ADD CONSTRAINT DF_report_create_dt DEFAULT getdate() FOR create_dt;</create>
    <drop></drop>
  </database-object>

and I could add a trigger in the same way for an update_dt type of field. This seems better than supplying explicit insert and update statements that use getdate().

Andrew Hanson · Accepted Answer · 2009-07-17 21:23:27Z

4

I alway prefer to use the NHibernate Event system to set my audit properties like created date or update date. (See event system documentation here).

I prefer this approach because it keeps the logic out of my database layer but also it gives me the ability to have a single location in my code that is responsible for setting these values. And if I have a common base class for all my entities then I can even guarantee consistent behavior throughout my domain.

answered Jul 17, 2009 at 21:23

Andrew Hanson

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3 Comments

dotjoe Over a year ago

The event system seems cool. I'd still prefer to use the db's date and I think I could do it by simply using a "select getdate()" to fetch the current date from db. This is the way to go, I don't want to copy that same logic to every table with those fields.

dotjoe Over a year ago

thanks, I went the events route. very nice! now I need to figure out how to inherit mapping files...

Andrew Hanson Over a year ago

Have you looked at fluentnhibernate.org for defining your mappings? If you're just looking at mapping inherited classes you can use the subclass element.

JleruOHeP · Accepted Answer · 2014-10-28 06:06:32Z

2

this is an answer on a thread for Hibernate... it should port over to nHibernate without changing it...

https://forum.hibernate.org/viewtopic.php?f=25&t=996901&view=previous

please see the last post.

Failing that, i always generate the "date created" of an object in the constructor of the class:

public class MyClass
{
    private DateTime createdDate;

    public MyClass()
    {
        createdDate = DateTime.Now;
    }
}

edited Oct 28, 2014 at 6:06

JleruOHeP

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answered Jul 17, 2009 at 19:40

Alex

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3 Comments

dotjoe Over a year ago

I guess it's just too database specific. I suppose I'd have to use the custom update query to handle an update_dt column. I'll probably just edit the create scripts for the create_dt columns.

dotjoe Over a year ago

Could someone explain why it's better to do it in the domain? I can only think of bad things such as the wrong system time and it's never going to be as exact as getdate().

Groxx Over a year ago

@dotjoe: Sure. It's partially subjective, but likely the best reason is that this way your object before-save represents a stable state, and doesn't change after-save (except maybe for the ID column, if DB-generated). If all your defaults are in the DB, then you must save the object to get useful values - if they're in the domain, on initialization, they're always there.

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