Comments on: Mapping Strings to Booleans Using NHibernate’s IUserType

By: FluentNhibernate: map byte enum as char | trouble86.com

FluentNhibernate: map byte enum as char | trouble86.com — Sun, 23 Oct 2011 13:26:53 +0000

[...] implement your own type conversion using IUserType interface. Example how to do that can be found here or [...]

By: eric swann

eric swann — Sun, 30 May 2010 23:05:53 +0000

Cool, glad I found this article Ray, I was just trying to do a wierd date conversion from our DB, I think this approach is what I’m looking for.

By: Rune

Rune — Mon, 22 Dec 2008 14:33:51 +0000

Just spotted this post. I have a similar problem and this solution does not seem directly applicable. I am from Denmark which means that instead of using Y/N in the database my predecessors opted for J/N. Can I somehow still use type=”YesNo” or do I have to use your YesNoType class?

By: Ray Houston

Ray Houston — Mon, 24 Mar 2008 11:10:14 +0000

@Matt – dang! How did I miss that? Anyway, thanks for pointing that out.

By: Matt

Matt — Mon, 24 Mar 2008 09:22:41 +0000

This is already built into NHibernate.. do type=YesNo

http://www.hibernate.org/hib_docs/nhibernate/1.2/reference/en/html_single/#mapping-types-basictypes

By: Ray Houston

Ray Houston — Sun, 23 Mar 2008 21:05:45 +0000

@Ken – I think we’re talking about two different things.

In my entity I may have a property like
public bool Active { get; set; }

In the database, the column is a string (because it’s legacy). My custom IUserType only shows up in the NH mapping and no where else. NH invokes it for me. It expects a string to come out of the database and then converts it to a bool (and vise versa going the other way). This all happens under the hood and my domain classes never know that it’s stored as a string in the database.

I’m going to post another example which might clear things up a bit.

By: Ken Scott

Ken Scott — Sun, 23 Mar 2008 19:00:49 +0000

So, the classes that you have talking directly to NHibernate are just a form of mapper or DTO class? Interesting…

How much churn do you have in your model that forces you to update the intermediate layer and/or the database? Do you have some sort of reflection/code generation to create an entity class from a DTO and vice versa?

By: Ray Houston

Ray Houston — Sun, 23 Mar 2008 14:47:46 +0000

@Ken – that’s the cool thing about this. My domain doesn’t reference my YesNoType. It my domain, I use plain old booleans. It might be less confusing if I had named this class YesNoMapper. It’s used for translating the database types, to .NET types. The .NET type can be anything you want as long as you supply the logic here to translate it.

By: Ken Scott

Ken Scott — Sun, 23 Mar 2008 14:32:11 +0000

Once you have created this user type and reference it in your Domain model, is there any way to not have a reference to NHibernate in the Domain model?

I’ve done something similar (created a user type for the version column to allow mapping of a SQL Server rowversion column to something other than Byte[]). It works fine, but I feel “dirty” seeing that reference to NHibernate in the model.

Do I need to just get over it?

Thanks,
Ken Scott