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    <p>You're doing something wrong.</p> <p>What you are trying to do is to change the type of an object. You can't do that in .NET or in Java. That simply doesn't make sense. An object is of exactly one concrete type, and its concrete type cannot be changed from the time the object is created until the time the object is destroyed (black magic notwithstanding). In order to accomplish what you are trying to do, but with the class hierarchy you laid out, you would have to destroy the customer object which you want to turn into a tier-one customer object, create a new tier-one customer object, and copy all the relevant properties from the customer object to the tier-one customer object. That is how you do it with objects, in object-oriented languages, with your class hierarchy.</p> <p>Obviously, the class hierarchy you have isn't working for you. You don't destroy customers in real life when they become tier-one customers! So don't do it with objects either. Instead, come up with a class hierarchy that makes sense, given the scenarios you need to implement. Your use scenarios include:</p> <ul> <li>A customer who previously is not tier-one status now becomes tier-one status.</li> </ul> <p>That means you need a class hierarchy which can accurately capture this scenario. As a hint, you should favor composition over inheritance. That means, it may be a better idea to have a property named <code>IsTierOne</code>, or a property named <code>DiscountStrategy</code>, etc., depending on what works best.</p> <p>The entire purpose of NHibernate (and Hibernate for Java) is to make the database invisible. To allow you to work with objects natively, with the database magically there behind the scenes to make your objects persistent. NHibernate will let you work with the database natively, but that's not the type of scenario which NHibernate is built for.</p>
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    1. PONHibernate - Changing sub-types
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    1. USyfeldblum
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    1. COI liked this answer, but felt David's was worded slightly better so I accepted his. Still, many thanks for the good answer - which I've up-voted.
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      1. USAndy Whitfield
 

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