Gill CleerenMicrosoft Regional DirectorMicrosoft MVP ASP.NETOrdina Belgiumwww.snowball.be - www.codeflakes.net gill.cleeren@ordina.be

Working with Data and Web Servicesin Silverlight 2

Get to know the audience…

Is this Silverlight?

Agenda

• Introduction• Building our first Silverlight/WCF application• Services that describe themselves• Services that don’t describe themselves• Accessing RSS/Atom feeds• Summary

Applications interact with the outside worldProduct catalog

Search stringProduct

databaseProduct information

In-Browser Application

PublicInternetmashup APIs

ExistingIntranetservices

New servicesyou build

RSS/AtomFeeds

ImagesSoundsVideos

Many Types of Outside Data

A Bit of History: Silverlight 1.0

PublicInternetmashup APIs

ExistingIntranetservices

New servicesyou build

RSS/AtomFeeds

ImagesSoundsVideos

JavaScript

HTML

?

AJAX (XmlHttpRequest)

1.0

<XAML/>

2

Managed Code (C#/VB)

The Story Today: Silverlight 2

PublicInternetmashup APIs

ExistingIntranetservices

New servicesyou build

RSS/AtomFeeds

ImagesSoundsVideos

HTML

Question 1:

What does the client code look like?

Managed Code (C#/VB)

2

New servicesyou build

Question 2:

What is the recommended way to create services for Silverlight?

Using a Custom Service from Silverlight

ServiceProductdatabase

DEMO

Recap: Required Steps

WCFService

• 1. Create the Service• 2. Define what it does

• 3. “Add Service Reference”• 4. Use the Service!

Creating a Service for Silverlight“Add New Item” (in Web Site / Web App)

“Silverlight-Enabled WCF Service”

Temporary for Beta1:• “Add New Item” “WCF Service”• Change wsHttpBinding basicHttpBinding in config

basicHttpBinding <endpoint contract=“IShoppingService” binding=“wsHttpBinding”…>

Defining the Contract• [ServiceContract] for the service class (interface in

Beta1)• [OperationContract] for methods (in the interface in

Beta1)• [DataContract]/[DataMember] for data types[ServiceContract]

public class ShoppingService {[OperationContract]Product[] GetProducts(string searchString){ /*... Implementation ... */ }

}

[DataContract] public class Product {

[DataMember]public string description;[DataMember]public string pictureUrl;

}

Nothing Silverlight-specific

Regular WCF code!

Adding a ReferenceIn the Silverlight project: “Add Service Reference”• “Discover” button will find services in solution• Can also give external URL

Creating the Proxy

var proxy = new ShoppingServiceClient();

• Default address chosen if no parameters given• Can pass in address manually• But what if the service moves?• Configuration support after Beta1• No need to recompile Silverlight client code if service moves• Can reuse one Silverlight app for many services

Making the Call

• Only asynchronous calls supported• Set up GetProductsCompleted event• “Tab,Tab” in Visual Studio

• Call GetProductsAsyncvar proxy = new ShoppingServiceClient();proxy.GetProductsCompleted +=

new EventHandler<GetProductsCompletedEventArgs>(proxy_GetProductsCompleted);

proxy.GetProductsAsync(“book”);

void proxy_GetProductsCompleted(object sender, GetProductsCompletedEventArgs e){

// Process response…}

Data Binding to Services

• All generated types/collections support data binding• Future Possibility:

Advanced data binding to services (XAML-only)

E.g. <GetProductsDataSource />

What we covered so far…

2

PublicInternetmashup APIs

ExistingIntranetservices

New servicesyou build

RSS/AtomFeeds

ImagesSoundsVideos

But what about the client code for other service types?

Approach #1:"Add Service Reference"

Metadata-driven, with Intellisense

Services that describe themselves

SOAPservices in the enterprise

Services for your Silverlightproject

SQL ServerData Services*(Astoria)

SOAP serviceson the Internet

Computer-ReadableMetadata

(e.g. WSDL)

AutomaticProxy

Generation

WCF

Demo:Accessing the Live Search APIfrom Silverlight in an automatic way

Add Service Reference

Works with:• Any “simple” SOAP service (e.g. Live Search)• SOAP 1.1 • Server-side may be JAVA, WCF, ASMX, etc.• A few restrictions (e.g. SOAP Faults not supported)

• Future Possibility: SQL Server Data Services (Astoria)

Can’t talk to just any service:Silverlight-Wide Cross-Domain Restrictions…

Cross-Domain Restrictions

Silverlight does not allow applications to cross domain boundaries by default:• MySite.com/silverlightApplication.xap

cannot call SomeOtherSite.com/someService.svc

• SecurityException if you try

Silverlight allows the calls if target site opts in• How do services opt in?• When should services opt-in?

Cross-Domain Policy Files

Silverlight looks for two policy files:• Silverlight policy: clientaccesspolicy.xml• Adobe Flash policy: crossdomain.xml• Already used by

All public services that work with Flash will also work with Silverlight!

Cross-Domain Policy Files

<?xml version="1.0" ?> <cross-domain-policy>  <allow-access-from domain="*" />   </cross-domain-policy>

<?xml version="1.0" encoding="utf-8" ?> <access-policy> <cross-domain-access> <policy>

<allow-from>  <domain uri="*" />   </allow-from>

<grant-to>  <resource path="/" include-subpaths="true" />   </grant-to>  </policy>  </cross-domain-access></access-policy>

Approach #2:Write the Code Manually

“A service call is just an HTTP request”

Human-Readable Documentation Only

Services that don’t describe themselves

RESTServices

“Mashup APIs” “Web APIs”

JSONServices

“POX”(Plain Old XML)services

Human-ReadableDocumentation

SomeManual

Work Required

1. Build a URL2. Make a request3. Work with request/response data (XML or JSON)

Demo:Accessing Flickr from Silverlight

Manually Issuing Requests

Code was exactly as in the regular .NET Framework!Good news for existing .NET developers

Some Silverlight-specific things to be aware of…

Manually Issuing Requests

• Build a URL• What are the allowed protocols?• Where can I connect to?

• Make a Request• How do I make a request?

• Working with Request/Response Data• How do I work with XML?• How do I work with JSON?

Manually Issuing Requests

• Build a URL• What are the allowed protocols?• Where can I connect to?

• Make a Request• How do I make a request?

• Working with Request/Response Data• How do I work with XML?• How do I work with JSON?

Allowed URLs

• HTTP and HTTPS• Some restrictions on HTTPS, cross-scheme• A few of these will go away after Beta1

• Subject to cross-domain rules• Must have policy file if not local URL

• No ftp:// or file:// URLs

Manually Issuing Requests

• Build a URL• What are the allowed protocols?• Where can I connect to?

• Make a Request• How do I make a request?

• Working with Request/Response Data• How do I work with XML?• How do I work with JSON?

Making HTTP Requests

• WebClient• Simple to use• Limited functionality

• HttpWebRequest• Access to all features

Manually Issuing Requests

• Build a URL• What are the allowed protocols?• Where can I connect to?

• Make a Request• How do I make a request?

• Working with Request/Response Data• How do I work with XML?• How do I work with JSON?

Working with XML

• XmlReader/XmlWriter• Linq to XML

• XmlSerializer

static void w_DownloadStringCompleted(object senderDownloadStringCompletedEventArgs e) { XElement x = XElement.Parse(e.Result); foreach (photo in x.Elements("photo")) { //... } }

The JSON Data Format

• “JavaScript Object Notation”• Easy and fast to parse in JavaScript in browsers

• Often no real reason to use it for SL, except…• Reusing existing services built for AJAX pages• Smaller message size

(but binary XML is a future possibility)

Example:{“Person”:{“name”:”john”,”age”:42}}

Approach #3:Use Built-In Classes

… for RSS/Atom feeds

Consuming Feeds

Atom 1.0Feeds

RSS 2.0Feeds

AtomPublishing(Future?)

Conform to a Standard

Built-in classes

to work withsuch services

SyndicationFeed feed = SyndicationFeed.Load(…)

foreach (SyndicationItem item in feed){ //Do something with item}

Demo: Accessing my blogs RSS feeds from

Silverlight

Syndication Support in Silverlight

• Protocols• RSS 2.0, Atom 1.0• Future possibility: Atom Publishing Protocol

• Essentially the same as in .NET 3.5• SyndicationFeed, SyndicationItem, etc.• Can read / write feeds

• Subject to same cross-domain restrictions, etc.• Use HttpWebRequest/WebClient, then Syndication to parse

Summary: What We Covered

• Creating Services for Silverlight• Creating and consuming WCF services• Securing local services• Creating public services (safe for cross-domain)

• Accessing Services that Describe Themselves• “Add Service Reference”

• Accessing Services that Don’t Describe Themselves• WebClient / HttpWebRequest, manual work

• Accessing Feeds• RSS/Atom

Resources

Silverlight: www.silverlight.net silverlight.net/blogs/jesseliberty/ timheuer.com/blog/www.silverlightcream.com Personal blogs:www.snowball.be www.codeflakes.net Email: gill.cleeren@ordina.be

Q&(maybe)A

Gill CleerenMicrosoft Regional DirectorMicrosoft MVP ASP.NETOrdina Belgiumwww.snowball.be - www.codeflakes.net gill.cleeren@ordina.be

Thank you!