REST, JSON and RSS with Windows Communication Foundation 3.5

Rob WindsorObjectSharp Consultingrwindsor@objectsharp.com

Me.About

Visual Basic MVP

Senior Consultant with ObjectSharp Consulting

President of the Toronto Visual Basic User Group

Member of the MSDN Canada Speakers Bureau

Contact me via my blog

http://msmvps.com/windsor

WCF Overview

JSON Services

HTTP Programming Model

Syndication

Agenda

One-stop-shop for services

Consistent object model

First released with .NET Framework 3.0

Focus on the functionality, WCF takes care of the plumbing

Windows Communication Foundation

The ABCs of WCF

Client Service

MessageABC A B C

A B C

Address Binding Contract

(Where) (How) (What)

WCF Standard Bindings

Name Transport Encoding Interop

BasicHttpBinding HTTP/HTTPS Text Yes

NetTcpBinding TCP Binary No

NetPeerTcpBinding P2P Binary No

NetNamedPipeBinding IPC Binary No

WSHttpBinding HTTP/HTTPS Text, MTOM Yes

WSFederationBinding HTTP/HTTPS Text, MTOM Yes

WSDualHttpBinding HTTP/HTTPS Text, MTOM Yes

NetMsmqBinding MSMQ Binary No

NetIntegrationBinding MSMQ Binary Yes

WCF Services

WCF Overview

JSON Services

HTTP Programming Model

Syndication

Agenda

JavaScript Object Notation

Format for bridging JavaScript and objects

Easier for browsers than XML

ASP.NET AJAX & other AJAX toolkits use it

Other web-aware clients also (Silverlight, etc.)

var data = {“temp” : 59, “descr” : “cloudy”};

document.write (“The weather is “ + data.descr);

What is JSON?

WCF AJAX support in Visual Studio

Script manager, VS Project Templates

WCF automatically generates JS proxy

Usage pattern similar to existing one:

Add service to Script Manager control

Write JavaScript code to work with proxy

Configuration not required

Via the WebScriptServiceHostFactory (.svc file)

Works in ASP.NET Medium Trust!

WCF / AJAX Integration

JSON Services

WCF Overview

JSON Services

HTTP Programming Model

Syndication

Agenda

Embrace the URI

Segments map to application logic

HTTP GET is special

GET is idempotent (View It)

Multiple GETs to a URI should produce the same (or similar) results

PUT / POST / DELETE do “stuff” (Do It)

Content-type header is the data model

Image, XML, JSON, etc.

Web Concepts (REST)

objectsharp.com/artists/Flaming+Hammer?album=HitMeobjectsharp.com/artists/Northwind?album=Overdone

objectsharp.com/astists/{artist}?album={album}

objectsharp.com/artists/Flaming+Hammer/HitMeobjectsharp.com/artists/Northwind/Overdone

objectsharp.com/artists/{artist}/{album}

The Web, the URI, and Apps

System.UriTemplate

Type for modeling URI to application semantics

Can “bind” data to a template, output a URI

Can “match” a URI to a template, retrieve data

System.UriTemplateMatch

Returned from UriTemplate “match” operations

Can get relative paths and wildcard segments

System.UriTemplateTable

For “binding” a URI to a group of UriTemplates

Modeling a URI in .NET 3.5

Uri address = new Uri(“http://localhost:2000”);

UriTemplate template =

new UriTemplate(“{artist}/{album}”);

Uri boundUri =

template.BindByPosition(address,

“Northwind”, “Overdone”);

UriTemplateMatch match = template.Match(address,

boundUri);

String bandName = match.BoundVariables[“artist”];

Roundtrip Data in a URI

Simple URI-to-application mapping

[OperationContract]

[WebGet(UriTemplate=“/Image/{artist}/{album}”)]

Stream GetAlbumImage(String artist, String album);

[OperationContract]

[WebGet(UriTemplate=“/Image?name={artist})]

Stream GetMainImage(String artist);

URIs in WCF Contracts

All HTTP verbs are first class citizens

GET, POST, PUT, etc.

“View It” vs “Do It” separation mimics web

[OperationContract]

[WebGet(UriTemplate=“/Image/{bandName}/{album}”)]

Stream GetAlbumImage(String bandName, String album);

[OperationContract]

[WebInvoke(METHOD=“PUT”)] // {PUT, POST, DELETE}

void AddAlbum(AlbumInfo albumInfo);

HTTP Verbs in WCF Contracts

HTTP headers can indicate

Accepted data formats (Request)

The format of the returned data (Response)

Common header names:

Accept (Request), Content-Type (Response)

Small sampling of varieties:

text/html, text/css,

image/gif, image/jpeg,

application/atom+xml, application/json,

video/mp4

Data Formats and the Web

WebOperationContext.Current provides access to incoming request headers

Can also set outgoing response headers

Some are shortcut for easier use

Stream GetAlbumImage(String bandName, String album){

Stream stream; // get the image from somewhere

WebOperationContext.Current.OutgoingResponse.ContentType =

“image/jpeg”;

return stream;

}

Specifying Data Format in WCF

WebHttpBinding endpoint on a ServiceHost

Add WebHttpBehavior to the endpoint

Use WebServiceHost/Factory in most cases

Web endpoints do not support WSDL

Works in ASP.NET Medium Trust!

Hosting / Binding

View It and Do It

Level-set

JSON Services

HTTP Programming Model

Syndication

Agenda

Syndications are more than news and blogs

Representation of any set of data

Usually slowly changing

Unified object model for RSS and Atom

SyndicationFeed / SyndicationItem

Feeds are service operations

Consume as a service or as document

Syndication Goals in .NET 3.5

Single stop for syndications

Create and Consume with or without WCF

Easy to use object model

Transport Agnostic

Supports syndication extensions

Format Agnostic

RSS 2.0 & ATOM 1.0, others possible

Works in ASP.NET Medium Trust!

Syndication in .NET Fx 3.5

[ServiceKnownType(typeof(Atom10FeedFormatter))]

[ServiceKnownType(typeof(Rss20FeedFormatter))]

[ServiceContract]

interface IAlbumSyndication {

[OperationContract]

[WebGet(UriTemplate=“Images/{format}")]

SyndicationFeedFormatter<SyndicationFeed>

Feed(String format);

}

Syndication Contracts in WCF

Syndication with PictureServices

Simple HTTP service development

SOAP and POX from the same contract

JSON messaging capability

Simple syndication – really!

Built on WCF

extensibility points

from .NET 3.0

Web Centric Features in WCF 3.5

Resources

Microsoft WCF Community Site

http://wcf.netfx3.com/

PictureServices Samples

http://www.cloudsamples.net/pictureservices/

The EndPoint on Channel 9

http://channel9.msdn.com/shows/The_EndPoint

Justin Smith’s Blog

http://blogs.msdn.com/justinjsmith/

Steve Maine’s Blog

http://hyperthink.net/blog/

Getting Started with WCF

http://msdn2.microsoft.com/en-us/vbasic/bb736015.aspx