CODEWITHSUNDEEP
nhibernate
FBryant87
FBryant87

Reputation: 4595

NHibernate - Add new property to class

I'm a little confused about what goes on behind the scenes in NHibernate when I add a new property to a class.

When I add a property 'Price' to an 'Item' class, my application throws an exception when retrieving Item objects because this new property isn't in the database:

[SqlException (0x80131904): Invalid column name 'Price'.]

Am I supposed to manually add a column to my DB table everytime I declare a new property in a class?

Upvotes: 2

Views: 2403

Answers (2)

Radim Köhler
Radim Köhler

Reputation: 123861

In general, we can use configuration setting for updating our DB schema whenever ISessionFactory is created:

<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
    <session-factory>
       <property name="hbm2ddl.auto">Update</property>

Check Table 3.2. NHibernate Configuration Properties

We can do it even in our own code:

How to update database table schemas with NHibernate schema generation?

(snippet from Q & A above)

_cfg = new Configuration();
_cfg.Configure();
_cfg.AddAssembly(Assembly.LoadFrom("DataLayer.dll"));
var update = new SchemaUpdate(_cfg);
update.Execute(true, false);

Summary, we can set our Factory to update schema, whenever such Factory is created. It could be used in DEV, but I would say, in DEV only...

Upvotes: 1

iakobski
iakobski

Reputation: 1274

The short answer is: yes, you are.

The class that you're asking nHibernate to map to a table in the database must only have properties that exist as columns in that table. If you want a new property in that class then you need to add a column in the table.

On the other hand, if you want a "Price" property for the Item that's not persisted in the database, then you would have a different class in the application, not under the control of nHibernate, which contains an object of class "Item", with its own "Price" property.

Upvotes: 1

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