Hello WCF RIA ServicesAn introduction to RIA Services

Gill CleerenMicrosoft Regional Director

Silverlight MVPOrdina Belgium

Glad to meet you...• Gill Cleeren• Microsoft Regional Director• Silverlight MVP• Telerik Insider & MVP• .NET Architect @Ordina (www.ordina.be) • Speaker (TechDays BE-NL-UK-SE-CH..., TechEd Berlin, DevDays, NDC Norway,

Spring Conference UK, SQL Server Saturday Switzerland...)• Visug user group lead (www.visug.be)• Author (Silverlight 4 Data and services cookbook)• www.snowball.be - gill@snowball.be - @gillcleeren

Agenda• Part 1: Introduction to WCF RIA Services• Part 2: The basics of RIA Services• Part 3: Concepts explained• Part 4: What about MVVM?• Part 5: Let’s validate!

PART 1: INTRODUCTION TO WCF RIA SERVICES

Database

Web servic

e

TrustBoundary

Data acces

s layer

App logic

App logic

View

The situation of the problem…

What is WCF RIA services exactly then?

Framework: WCF RIA Services provide end-to-end use of dataRetrieved by DAL of choice, shaped in BLL, annoted for validationData and metadata can flow over tiers through controlled set of operations

Tools: build multiple tiers togetherCode is generated on the client

Services: common services such as authentication can be reusedBased on ASP.NET foundation

Framework, tools and services withprescriptive pattern for n-tier applications

Why WCF RIA Services?• Less plumbing code to write• Prescriptive approach for working with data on

the client side• Makes working with WCF easier, hides details• Makes using LINQ possible in n-tier scenarios• Client side framework for service calls, validation

and security

• End-to-end view of an application: – Framework– Tooling – Services

• Prescriptive approach to app logic • DAL-neutral and targets multiple presentation technologies• Make RIA development as productive as ASP.NET development• .NET on server and on client

Important design principles

Being neutral

AppLogic

DatabasesADO.NET,ORMs (LTS, EF, …)

Lists/ObjectsRepository(NHibernate, …)

ServicesREST/SOAP(Azure, …)

.NET ClientsSilverlight,WPF (hopefully phone)Standards ClientsJavaScriptServer RenderingHTML, Sitemaps

ServicesSOAP, XML,JSON, OData Unit Test

Code

How do I get WCF RIA Services?• If you have Silverlight tools installed, you have RIA

Services already • Additional download: RIA Services Toolkit

– Adds support for other endpoint types (SOAP, JSON)– ASP.NET support for consuming domain service in process

• WCF RIA Services SP1– We’ll look at this later!

PART 2: THE BASICS OF WCF RIA SERVICES

The Dev Process: Server-Side

1 2 3 4

Create Business

Application

Create Entity Model

Create Domain Service

Add/generatequeries

5Modify

Metadata

DEMOCreating the server-side

The Dev Process: Client-Side

Use Data Sources window

2

Drag on the interface

31

Generate DomainDataSource

Success!

4

Note that this is just

one way of using RIA services

DEMOCreating the client-side

PART 3: CONCEPTS EXPLAINED

Concepts of RIA Services

Code generation

Domain Data source

ValidationMeta data

Querying

Shared code

Authentication

WCF RIA SERVICES

Domain Context

Server-side

Domain Service

Metadata Classes

Validation Attributes

Security Attributes Shared Code

Use query operations to read data

• Inside the service, we can query data– Query operations return object, IEnumerable<T> or

IQueryable<T>• IQueryable<T> and LINQ provider are required if we want to use

deferred execution

– Based on convention (GetXXX, RetrieveXXX…)• If convention isn’t possible, use Query attribute• Other attributes exist:

– IsComposable=false when returning single entity– ResultLimit to constrain maximum items returned to client

Let’s defer things• The use of IQueryable<T>: Deferred Execution

– RIA Services serializes the expression tree from the client the server

– LINQ operations specified by the expression tree are executed on the server

– When the underlying provider supports it (i.e. Entity Framework and LINQ to SQL), deferred execution goes all the way to the DB

Querying Relations• What if we want to return related entities in one

go?– Load all Hotels for a City– Step 1 (Entity Framework)

• ObjectContext.Cities.Include(“Hotels”)

– Step 2:• Entity metadata type needs [Include] attribute

on related property

Conventions can help us!• RIA Services uses naming conventions in domain service to

identify methods– Insert: InsertXXX, AddXXX, CreateXXX– Update: UpdateXXX, ModifyXXX, ChangeXXX– Delete: DeleteXXX, RemoveXXX– Where XXX is an entity type name

• If we want Dutch code (yes some people do that…), we can use Attributes– Insert, Update, Delete attributes

Metadata or buddy classes• Define a partial class for the entity type • Define a nested metadata class inside the entity type

– Not required, but convention– “Buddy class”

• Add a MetadataType attribute on the entity partial class to tie in the metadata type• Add attributes to properties on the metadata type that match the entity properties• Those attributes show up on the client entity type or influence entity transmission

– Validation– Include– Exclude– Composition

Client-side

Domain Context

Entity Query Entity Load Operation

Submit Operation

Client-side generated entities• On the client, entities get generated (code-generation)

– Entity Framework or LINQ to SQL entities supported automatically

– POCOs must follow certain conventions• Must have a [Key] property• Relation properties must have an [Association] attribute to

indicate the related property type’s key fields• Need [Include] attribute on properties to child entity

collections or single entities to have them serialized

Loading Data on the Client• Option 1: what you CAN do: the DomainDataSource

– Allow you to execute a DomainContext method to query data• Including updates• Happens async

– Drag/drop data binding is VS 2010 generates XAML DomainDataSource and Grid

• (we’ve seen this in the demo)

– Supports parameterized queries– Supports sorting, grouping, filtering, pagingNot a good fit with MVVM

• Puts query “logic” into the view

Loading Data on Client• Option 2: What you SHOULD do: DomainContext.Load()

– Pass an EntityQuery<T>– Can modify the expression tree on client if target method in

DomainService returns IQueryable<T>– Executes asynchronously– Bind to entity collection for automatic update via INotifyCollectionChanged– Pass async callback to be notified and work with results or handle errors

yourself– Can work with returned LoadOperation<T>

for async notification as well

Update Operations• Implicit unit of work:

– Entity changes are cached in the client DomainContext until SubmitChanges called

Contains an EntityContainer for each entity type that tracks changes

• Sent as a batch to the service– Including original version for optimistic concurrency

• Service executes batch, calling Insert, Update, and Delete methods with one entity per method call

Security• Authentication• Roles• User profile• Declarative: class / method-level• Integrated into Query / Submit processing• All based on ASP.NET infrastructure

What is added with SP1?Cloud Ready

Complex Type

Support

Shared Entities

T4 Templates

DomainCollection

View

DEEP-DIVE DEMO

PART 4: WHAT ABOUT MVVM?

RIA Services and MVVM == BFF• Server-side: no changes, just create your services as

normal• Client-side:

– The generated entities are your model objects• They already implement INotifyPropertyChanged

– You get DomainContext • Your gateway to the web services• Change tracking

– Don’t use the DomainDataSource!

MVVM DEMO

PART 5:VALIDATION WITH WCF RIA SERVICES

Validation in Silverlight• Validation in Silverlight is based on the concept of data binding• Several options exist:

– IDataErrorInfo– INotifyDataErrorInfo

• INotifyDataErrorInfo supports async validation– When we set a value, it may be OK client-side but not server-side– An event is raised if server-side validation fails– Silverlight watches for this event being raised

• RIA Services Entity base class provides the implementation

INotifyDataErrorInfo interface

public interface INotifyDataErrorInfo {

bool HasErrors { get; } event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged; IEnumerable GetErrors(string propertyName);

}

RIA Services Validation OptionsWe have 3 options:1. DataAnnotations attributes2. Server update method exceptions3. Client async service method calls

Data Annotations Attributes• Live in System.ComponentModel.DataAnnotations namespace

– Also used by ASP.NET MVC and Dynamic Data• Contains a few standard attributes:

– [Required]– [Range]– [RegEx]– [StringLength]

• And then there’s the Custom one…– [CustomValidation]– Define static method with appropriate signature:public static ValidationResult ValidateCityName(string

newCityName, ValidationContext context)

Data Annotations how-to• WCF RIA Services will automatically evaluate data

annotation attributes on both client and server side• For Entity Framework generated types on server, define

metadata class and put attributes on its properties• Client generated entities contain same attributes• CustomValidation methods must be put in a .shared.cs

file so they get copied to the client side

Server Validation Exceptions• Some things have to be evaluated on the server

– Can wait until update batch is submitted to evaluate validation rules server side

– Throw ValidationException from insert, update, or delete method– RIA Services automatically associates the error with the individual

entity and hooks into the validation client side– Will still be raised as an exception from the SubmitChanges

method, must handle– Can also inspect properties of the SubmitOperation

• EntitiesInError collection

Client Async Calls• Expose [Invoke] methods on domain service• Call method with value to be changed, get

back result• Set validation errors manually

– Entity.ValidationErrors.Add

VALIDATION DEMO

Summary• RIA services opens up oppurtunity to build n-

tier apps with ease• Built on power of WCF• Key concepts explained• Works in combination with MVVM• Supports several validation types

Q&(HOPEFULLY)A

THANKS!

Hello WCF RIA Services

Gill CleerenMicrosoft Regional Director

Silverlight MVPOrdina Belgium

© 2008 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

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