Validation Rules
Every business application must incorporate some kind of business logic and validate the response received from the user. There are a few ways to incorporate this logic through your application, which involve a mix of client and server side validations. This often means you will have some validation in your UI layer as Field validators and some logic in your business tier, where it is just not possible to bring to the UI such as verifying a date range does not overlap another set, or something which needs to access the database to verify against. The Validation Rules library attempt to unify this disparate approach to validation, and to automate some of the simpler validation logic such as required fields and field length validation. Instead of putting validation through the tiers, we can simply implement IValidation on the business object. This interface attaches a meta list of rules to the entity which we can build in the business layer and will propagate through down to th...