Microsoft Silverlight Applications Need Data...and Here's How to Get It!Gill CleerenMicrosoft Regional Director Benelux / MVP ASP.NET.NET Software architect Ordina Belgiumwww.snowball.be

About Gill

• .net architect Ordina (ordina.be) • Microsoft Regional Director (theregion.com) • MVP ASP.net• Writing:

.net magazineBlogs MSDN

• Speaking: TechDaysUsergroups(Visug, Biwug, Besug)Ineta speaker

• Blog: www.snowball.be • Email: gill.cleeren@ordina.be• Twitter: gillcleeren • MSN: gillcleeren@hotmail.com

Agenda Silverlight and data• Building a service for Silverlight• Accessing WCF services• Accessing REST services• Accessing RSS feeds

Applications interact with the outside world

Product 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

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”

“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 GetProductsAsync

var 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

Accessing the Live Search APIfrom Silverlight in an automatic way

Demo

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)

Accessing Flickr from SilverlightDemo

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 URLWhat are the allowed protocols?Where can I connect to?

• Make a RequestHow do I make a request?

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

Manually Issuing Requests

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

• Make a RequestHow do I make a request?

• Working with Request/Response DataHow 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}

Accessing my blogs RSS feeds from Silverlight

Demo

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

Question & Answer

Microsoft Silverlight Applications Need Data...and Here's How to Get It!Gill CleerenMicrosoft Regional Director Benelux / MVP ASP.NET.NET Software architect Ordina Belgiumwww.snowball.be

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