Silverlight 3 Tier application validation

I am going to develop the 3 tier application using Silverlight + 开发者_运维知识库WCF + ORM

Now my question is if I use ORM at database layer then how can I expose the classes at Presentation, Business layer to do Client-Side validation ?

If you used WCF RIA services instead of plain Silverlight WCF, you can attribute the properties of your data objects (in the associated metadata classes RIA creates for you).

This allows you to add basic validation rules, or even custom ones, that runs on both the server and client.

Using WCF RIA Services via a library is the preferred way to organise projects so try this link: Walkthrough: Creating a RIA Services Class Library

Also:

• Using WCF RIA Services
• Creating Rich Business Applications using Silverlight 4 and WCF RIA Services
• Various Channel 9 Videos

Is is generally a bad idea to expose your business entities directly to the frontend. Not only is what fits your backend layer rarely a good fit for your frontend but you also run the risk of exposing security critical information to the client - which should never be trusted.

An approach that generally worked well for us is developing the Silverlight Frontend using the MVVM pattern and have your WCF Service Layer return DTOs that can be more or less directly mapped to the data requirements of a ViewModel. This also satifies one of the most important rules when developing intranet/internet client server applications and that is to keep roundtrips to a mimimum because a DTO tailored to the needs of a particular viewmodel can include all the relevant information at once.