and Web Services

Gill Cleeren

Microsoft Regional Director

Microsoft MVP ASP.NET

Ordina
Belgium

www.snowball.be

-

www.codeflakes.net


gill.cleeren@ordina.be


Working with Data
and Web Services

in 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 world

Product catalog

Search string


Product

database

Product information

In
-
Browser Application

Public

Int
e
rnet

mashup

APIs

Existing

Intr
a
net

services

New services

you build

RSS/Atom

Feeds

Images

Sounds

Videos

Many Types of Outside Data

A Bit of History: Silverlight 1.0

Public

Int
e
rnet

mashup

APIs

Existing

Intr
a
net

services

New services

you build

RSS/Atom

Feeds

Images

Sounds

Videos

JavaScript

HTML

?

AJAX
(
XmlHttpRequest
)

1.0

<XAML/>

2

Managed Code (C#/VB)

The Story Today: Silverlight 2

Public

Int
e
rnet

mashup

APIs

Existing

Intr
a
net

services

New services

you build

RSS/Atom

Feeds

Images

Sounds

Videos

HTML

Question 1:


What does the

client code

look like?



8

Managed Code (C#/VB)

2

New services

you build

Question 2:


What is the
recommended way to
create
services

for Silverlight?




Using a Custom Service from
Silverlight

10


Service


Product

database

DEMO

Recap: Required Steps

WCF

Service

•
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 Reference

In 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
GetProducts
Completed

event

•
“
Tab,Tab
” in Visual Studio

•
Call
GetProducts
Async


var proxy =
new

ShoppingServiceClient
();

proxy.GetProductsCompleted

+=


new

EventHandler
<
GetProductsCompletedEventArgs
>(proxy_
GetProduc
tsCompleted
);


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

Public

Int
e
rnet

mashup

APIs

Existing

Intr
a
net

services

New services

you build

RSS/Atom

Feeds

Images

Sounds

Videos

But what about the
client code

for
other service types
?


Approach #1:

"Add Service Reference"

Metadata
-
driven, with
Intellisense

19

Services that describe themselves

SOAP

services in the
enterprise

Services for

your Silverlight

project

SQL Server

Data Services*

(Astoria)


SOAP

services

on the Internet

Computer
-
Readable

Metadata

(e.g. WSDL)

Automatic

Proxy

Generation

WCF

Demo:

Accessing the Live Search API

from Silverlight

in an automatic way


21

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!




25

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”

26

Human
-
Readable Documentation
Only

Services that don’t describe
themselves

REST

Services

“
Mashup

APIs”


“Web APIs”

JSON

Services

“POX”

(Plain Old XML)

services

Human
-
Readable

Documentation

Some

Manual

Work
Required

1. Build a URL

2. Make a request

3. Work with request/response data (XML or JSON)


Demo:

Accessing Flickr from Silverlight

29

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 sender

DownloadStringCompletedEventArgs

e)


{


XElement

x =
XElement.Parse
(
e.Result
);




foreach

(photo in
x.Elements
("photo")) {


//...


}


}

The JSON Data Format

•
“
J
ava
S
cript
O
bject
N
otation”

•
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

39

Consuming Feeds

Atom 1.0

Feeds

RSS 2.0

Feeds

Atom

Publishing

(Future?)

Conform to

a Standard

Built
-
in
classes

to work with

such services

SyndicationFeed

feed =
SyndicationFeed.Load
(…)


foreach

(
SyndicationItem

item in feed)

{


//Do something with item

}

Demo:



Accessing my blogs RSS feeds from
Silverlight

41

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 Cleeren

Microsoft Regional Director

Microsoft MVP ASP.NET

Ordina
Belgium

www.snowball.be

-

www.codeflakes.net


gill.cleeren@ordina.be



Thank

you
!