MSDN Magazine - November 2008 - (Page 23)

JohN PaPa Data Points Cloud Gazing From Silverlight 2 Developers who use Silverlight have their or Visual Basic and leverage all your existing Services heads in the clouds, but can you blame experience against the .NET CLR. While the ASMX them? Obtaining data for rich Internet aplibraries included in Silverlight are a subset plications (RIA) from various types of Web Silverlight 2 of the overall .NET libraries, there is plenty WCF Client services is growing in prominence. Silverof functionality in Silverlight 2. For examApplication REST light apps can communicate with ASMX ple, the WebClient and HttpWebRequest Web services, Windows Communication classes are accessible from Silverlight and POX Foundation (WCF) Web services, Reprecan be used to interact with Web-based sentational State Transfer (REST) services, services by calling URIs. The data can then and plain old XML (POX) services. Wheth- Figure 1 Accessing Services from Silverlight be consumed using XmlReader objects or er these services are supplied by third parthrough LINQ to XML. ties or they are custom services hosted on the same server where Silverlight 2 added a large set of features for passing data between the Silverlight app resides, Silverlight can request data, consume services. The following features are all new to Silverlight 2: the data and pass data back and forth between the Silverlight cli• SOAP-based Web services can be accessed through proxy ent application and these types of Web services. classes. Based on questions I have been receiving, it’s clear that develop• REST-based Web service can be accessed. ers want to know more about calling services from Silverlight 2 ap• ADO.NET Data Services, a REST-based service that allows plications, the differences between using WCF, ASMX, and REST remote LINQ queries, can be accessed. services, and about how to consume the data that these services • Results can be retrieved using both JavaScript Object Notation expose. In this installment of Data Points, I will address some of (JSON) and XML from Web services. these questions and demonstrate how to deal with data services. • Duplex communications are supported through WCF (using There are plenty of third-party Web services that offer everything server push). from access to their APIs to storage of client-specific and custom • Cross-domain access is supported using either the clientdata. I’ll discuss the consuming and passing of data between Silaccesspolicy.xml file or the crossdomain.xml file. verlight applications and the cloud of services. I’ll also show how • Cross-domain network support is available using HTTP and data can be consumed using several XML parsing libraries. For Sockets. example, XML documents can be opened and iterated through or • Web service calls are initiated asynchronously. XML can be queried using LINQ to XML. Services such as Flickr, Amazon, Twitter, and Live Search all expose APIs that can be com- How is data passed from services to Silverlight 2? municated with through various Web service techniques. Here I’ll Figure 1 shows several types of services that Silverlight 2 can discuss some of these APIs and show how you can communicate access. Data can be passed between Silverlight 2 and these servicwith them using REST- and SOAP-based services. All examples in es as XML, JSON, or as scalar values. SOAP-based services allow this column are available in both C# and Visual Basic and can be themselves to be described, which, in turn, allows the data that downloaded from the MSDN Magazine Web site. they expose to be described. A Silverlight 2 client can access the data from SOAP-based services by creating a proxy to the service, How are Web services handled in Silverlight 2? which generates a class description for the exposed classes. This is a good question I like to start with, as it sets the basis for understanding why so many developers are using Silverlight 2 to inThis column is based on a prerelease version of Silverlight 2. All information is teract with Web services. Silverlight 1.x did not support code based on subject to change. the Microsoft .NET Framework, nor were there any .NET controls. Code download available at msdn.microsoft.com/magazine/cc135911. Silverlight 2 introduced a lot of full-featured functionality that blew Send your questions and comments for John to mmdata@microsoft.com. away previous limitations. Silverlight 2 allows you to write code in C# November 2008 23 http://msdn.microsoft.com/magazine/cc135911

Table of Contents Feed for the Digital Edition of MSDN Magazine - November 2008

Contents MSDN Magazine - November 2008 Toolbox CLR Inside Out Data Points Cutting Edge Security Briefs Test Your Security IQ Agile SDL Access Control Utility Spotlight RIA Test Run Wicked Code Foundations Team System End Bracket

MSDN Magazine - November 2008

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