Silverlight & WCF RIA Services: Strategies for handling your Domain Context - Part 1

This is the first in a two-part article series on the WCF RIA Services Domain Context.

Part 1: Introduction, instance strategies & first strategy

Part 2: Other instance strategies, pointers & conclusion 

This article series is accompanied by source code, which can be downloaded here.

Introduction

A lot of business applications that are being developed in Silverlight today are built with the help of WCF RIA Services. This should come as no surprise, as it’s a really powerful, extensible framework which provides us with a lot of features out of the box (validation, authentication, authorization, …) that otherwise would require quite a lot of custom code, workarounds & plumbing. In WCF RIA Services, you’re going to be working with a client-side Domain Context instance. This article will look into a few strategies on working with this Domain Context, and is accompanied by a demo & source code, which you can download here.

But let’s start with a short introduction on what a Domain Context actually is. 

What is a Domain Context?

When you create a new Domain Service & build your project, you’ll notice a Domain Context class (a class inheriting DomainContext) has been generated for you on the client (in a Silverlight class library project if you’re using a WCF RIA Services class library, or straight into your Silverlight project): one for each Domain Service. If you create a Domain Service named MyDomainService, you’ll get a generated Domain Context on your client named MyDomainContext, which inherits from the DomainContext class. It contains query operations to fetch data, collections of the entities you’re exposing through the Domain Service, submit and reject operations, … It provides a lot of functionality to help you with change tracking & interacting with the underlying Domain Service.

Those of you who are familiar with an object relation mapper (ORM), like the Entity Framework, will feel right at home: working with the WCF RIA Services Domain Context is quite similar to working with the Object Context you get when using the Entity Framework: you load data into the Context, the Context has collections of Entities you’re exposing through your Domain Service(s), it allows for change tracking on these entities, and you get your typical submit & reject-operations. Of course, you’re working in an asynchronous, service oriented environment when using WCF RIA Services: what actually happens when you submit the changes on your Domain Context is that that same context is rebuilt on the server side, and submitted once completely built.

As an example, we’ll assume we’ve got an Entity Model with a Category & Book object (cfr John Papa’s Bookstore Club example). A Book belongs to a Category, so one Category can have multiple Book objects: we’ve got a Navigation Property Books on our Category. When you create a Domain Service, BookDomainService, and select these 2 entities, WCF RIA Services will generate all the CRUD operations for you.

Read more: Silverlight Show

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