That's a great feature, I didn't even know it was there.

So I guess this lets you do:

var person = _session.Load <person(1);

Assert.AreEqual( "123", person.Attributes["SSN"] );

I assume that mapping properties into a dictionary is the primary use case -- very handy for multi-tenanted apps -- are their any other things you've used it for?

I guess my question would be how do you dynamically extend the entity? Putting some data in the xml document about your mapping doesn't seem very dynamic to me.

Putting some data in the xml document about your mapping doesn't seem very dynamic to me.

nor does adding a column to the database. Is there anyway you could show an example that uses a property bag in both the database and object model?

Hrr. I had to use Boo compiler to regenerate entities on-the-fly when adding fields instead of simply using dynamic component..

Thank you for this set of lectures about NHibernate features, Ayende.

Excellent stuff, a question on using an Attributes table comment. How would you make the Attributes property a simple dictionary?

Sorry Ayende, I was referring to Mike's comment. Could you show an example of how to map a property bag table (Name/Value Pair) in DB to an IDictionary Attributes property of a class?

Excellent Ayende thank you.

How can i solve this (see picture) problem with NHibernate? i have a superclass Question and a lot of subclasses, all with their own specific attributes. I don't want to create table for each class, because of perfomance. The solution is to make an QuestionDetail table with key, value columns where i can store names and values of all specific attributes from subclasses. How can i do it in NHibernate?

tweakers.net/.../full.jpg

Thanks, Ayende, it works :-)

I have added IDictionary <string,> Properties to my Question class to map key-value pairs. My mapping looks like this:

{map name="Properties" table="QuestionDetails" }

  {key column="QuestionID" /}

  {index column="Name" type="String" /}

  {element column="Value" type="String" /}

{/map}

How can i force NHibernate to use this mapping if I create new QuestionType (subclass) object? Now create a Question object as follows:

        Question sbq = new Question();

        sbq.attr1= "attr1value";

        sbq.attr2= "attr2value";

        sbq.Properties = new Dictionary

<string,> ();

        sbq.Properties.Add( "attr3", "attr3" );

        sbq.Properties.Add( "attr4", "attr4" );

And I'd like to have it so:

        QuestionType2 sbq = new QuestionType2 ();

        sbq.attr1= "attr1value";

        sbq.attr2= "attr2value";

        sbq.attr2= "attr3value";

        sbq.attr2= "attr4value";

Should I use discriminator? Or <subclass? If I use <subclass, than NHibernate just puts subclass attributes to the Question table, or in QuestionType2 table when using <joined-subclass
Thanks in advance :)