ASP'NET AJAX with Web Services

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ASP.NET AJAX with Web Services

• Noah Subrin
• Atlanta MS Pros
• Cutting Edge
• VB .Net Study Group
• November 5, 2007

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Speaker Biography

• Technical Lead SRA International
• MCSD and MCSD .Net
• Participates in developer community events in the
  Southeast
• Published several articles on www.sswug.org

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What we will discuss tonight

• Brief ASP .Net AJAX 1.0 overview
• AJAX Programming models
• Focus on Remote Services
• Web Services
• Page Methods
• Built in APIs

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Traditional Web Apps

• Web was originally designed for static pages
• Todays web is much more interactive.
• Client issues a request, the server returns HTML
  markup, and the entire page is refreshed
• Everything is done on the web server

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AJAX-Enabled Applications

• AJAX apps use a client side framework to make out
  of band calls to the server
• AJAX server side framework returns data to the
  customer that is primarily in the form of JSON
  but may be XML or other formats such as RSS, CSV
• Reduces bandwidth required and UIs are able to
  be redrawn using partial rendering
• More code is executed on the browser

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So What is ASP .Net 2.0 AJAX?

• Server side ASP 2.0 AJAX extensions that are
  installed in global assembly cache (GAC)
• Client side JavaScript libraries that can be used
  stand alone
• Visual Studio 2005 or Visual Web Developer are
  not necessary to use server side components (but
  they provide templates)

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AJAX Programming Models

• Partial Page Rendering
• Script Services
• Local web services
• Page Methods
• How to call external web services
• Authentication services
• Profile Web services

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Characteristics of AJAX services

• REST services (Representational State Transfer)
• Each URL represents the state of an object
  retrieved using an HTTP verb (GET, POST, PUT)
• Tied to the platform and domain where they are
  hosted
• Not SOA in truest sense
• Who uses REST ? Amazon, Yahoo and many others

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REST Web Services

• Predates the WS specs
• Typically easier to read than SOAP
• New operation can be exposed without updating web
  reference
• REST relies on HTTP verbs and URLs to express
  the operation
• Not a standard (like SOAP) or a protocol (like
  HTTP)
• Each operation has a distinct URL

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SOAP Web Services

• SOAP services are an XML based protocol SOAP
  services need an envelope, message, header, and
  body
• WSDL to describes the web service API
• XML Schema describes the call
• Uses a single URL
• Can support WS specs

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AJAX Web Services Demos

• Expose the web services to clients
• Calling web services from the client
• Fire and Forget
• Returns a Value
• Takes Parameters
• Handles an Error
• Lengthy Operation
• User Context and method Names
• Complex Types

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Why only Local Services?

• Security implications of cross site calls
• SOAP is harder to manage from client side
  JavaScript
• No XML parser is needed
• Support for JSON serialization which uses
  name-value pairs

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What about WCF Services?

• In ASP .Net AJAX 1.0 we are currently unable to
  call WCF services
• Support for WCF services calls from AJAX in Orcas
  will presumably be enhanced

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Page Methods

• Provide ability for client script to call a
  static method in an ASP .Net page as if it were a
  web service.
• Scoped within a page -cannot be called from a
  different page other than where they are defined
• Decorated with WebMethod attribute

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More on Page Methods

• All types will be JSON serialized
• Not enabled by default, to enable, we set the
  ScriptManager property EnablePageMethodstrue
• The page acts as a web service

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PageMethods Demo

• Writing to Session object from a PageMethod

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PageMethods vs AJAX Web Services

• From PageMethods we can access Session state, ASP
  .Net Cache, and User objects
• For PageMethods we dont have to create an .asmx
  web service
• Local Web services are callable from every page
• Web services are callable by SOAP based clients
• For both - dont include any critical business
  logic (replay attacks)

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Calling external web services

• Not included in ASP .Net AJAX Extensions 1.0
• New file type .asbx, which is an xml file
• It contains info on how to connect to a remote
  web service
• This is a Futures technology but it is possible
  to build manually using WebMethod or PageMethod
• Client calls its own server local server calls
  a remote server

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Application Services

• Forms Authentication
• Profile Information

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Forms Authentication

• We can use the MS AJAX library authentication
  service to verify credentials stored as part of
  the ASP .Net membership application service
• Server configuration is in web.config
• Server issues a ticket
• Client browser needs cookies enabled

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Forms Authentication Demo

• Restrict Directory Access
• JavaScript Functions
• Web.config settings
• Membership provider

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Profiles Web Services

• The profile service enables you to use the
  ASP.NET profile application service from client
  side JavaScript
• Must enable the Profile Service in the web.config
• By default, no profile properties are available.
  For each profile property that you want to make
  available in a client application, add the
  property name to the readAccessProperties
  attribute of the ltprofileServicegt element.

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Profile Services Demo

• Adding custom properties to a .Net 2.0 Provider

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Summary

• We can create and expose local web services to
  client side JavaScript
• We can use local web services or PageMethods
• We used JSON serialization
• We leveraged callback functions to update the
  pages
• We can call ASP.Net 2.0 Authentication and
  Profile services from client side JavaScript

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Additional Resources

• www.asp.net/ajax
• SOAP Specification httpwww.w3.org/tr/soap)
• REST Specification
• http//www.ics.uci.edu/fielding/pubs/dissertatio
  n/top.htm
• Introducing Microsoft ASP .Net AJAX by Dino
  Esposito
• Professional ASP .Net 2.0 AJAX by Matt Gibbs and
  Dan Wahlin

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Contact Info

• Email address
• support _at_federalsystems.net
• Blog blogs.federalsystems.net