A1256655664CBTFz

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• A Client-Side Environment for ASP Pages
• Dino Esposito
• Artis.Net
• desposito_at_artis.net

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Topics to be covered

• Rationale and ASP infrastructure
• ASP client-side infrastructure
• Implementation details
• Globals and business components

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Goals

• Find a technology for delivering content through
  both online and offline channels
• Web sites, portals
• CD, DVD, mobile devices, local desktop apps

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Off-the-shelf Choices

• (Dynamic) HTML
• Browser dependent
• Visual Basic
• Two fairly distinct apps (web, local)
• ASP
• Doesn't work without a web server

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Constraints

• Identical technology
• if not identical sources...
• The only redistributable must be the browser
• or a browser-like app
• "Re-use" as many skills as possible
• The more legacy, the better
• ASP without IIS or PWS
• Dual (on/offline) ASP pages

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ASP Fundamentals

• Run through an ISAPI extension under the control
  of IIS and MTS/COM
• The script code is parsed by IIS
• IIS populates the scripting's namespace with ASP
  intrinsic objects
• Request, Response, Session and the rest
• Nothing of the kind on the client
• Want to get rid of IIS?
• Need a client-side replacement...

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Call to Action

• A specialized browser
• Detect client-side ASP pages
• Manage for links and forms
• Emulator for the ASP object model
• No support for Session, Application and
  ObjectContext
• Do what IIS does with ASP pages
• Extract and process the code blocks
• Collect all the output and send it to the browser
• How to process script code?
• Windows Script interfaces or the Script control

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Topics to be covered

• Rationale and ASP infrastructure
• ASP client-side infrastructure
• Implementation details
• Globals and business components

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The Browser

• Must detect a local ASP page
• Treat it in a different manner
• Invoke a made-to-measure ASP parser
• Must redirect to local pages when relative URLs
  have been specified
• Must collect - and pass on to the server -
  information about forms
• Must prepare the correct (client-side)
  environment for ASP pages

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The Object Model

• Any piece of ASP code is processed on the client
  in the environment that the browser (not IIS) set
  up
• Browser is the IIS client-side counterpart
• The intrinsic ASP objects must have a client-side
  counterpart
• The browser is responsible for making objects
  called Response, Request, Session available to
  the scripts

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Scripting Namespace
IIS
ASPClient
VBS/JS parser
Response Request Server Session Application Object
Context
lt script gt
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Using the Script Control

• Implements the Windows Script interfaces
• Executes script code connecting to the script
  parser
• Allows you to customize the environment where the
  script executes
• Scripting namespace
• Allows you to insert global code
• Variables, functions

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Injecting Fake ASP Objects

• Write objects that mimic the behavior of the ASP
  intrinsic objects
• Same programming interface
• Same public name in the scripting namespace
• Just automation COM objects
• No matter the language
• No matter the progID
• No need for Session and Application
• Unless for multiuser local environments

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Topics to be covered

• Rationale and ASP infrastructure
• ASP client-side infrastructure
• Implementation details
• Globals and business components

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The Response Object

• The write method
• Cannot write a Response object with VB!
• The internal buffer
• Like working with ASP buffering always on
• The methods Clear and End

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Demo

• Using the ASPClient browser to open local ASP
  files using the Response object

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The Request Object

• Command-line arguments
• Expose a collection for
• QueryString
• Form
• ServerVariables

C\file.asp?Param1val1Param2val2
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The QueryString Collection

• Collects the parameters sent through GET commands
• IIS fills the collection by examining the HTTP
  command request
• ASPClient fills the collection by examining the
  command line
• What about forms?
• Accessed through name/value pairs

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Collection vs. Dictionary

• Collections are a set of values
• Indexes or keys to access
• Dictionaries are a set of name/value pairs
• Associative arrays
• QueryString is a dictionary
• In VB, use Scripting.Dictionary instead of the
  native Collection type

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The Form Collection

• Collects the parameters sent through POST
  commands
• IIS fills the collection by examining the HTTP
  command request
• ASPClient fills the collection by examining the
  command line
• What about forms?
• Accessed through name/value pairs

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Working with ltformgt

• The browser collects the value of the form's
  elements and sends them to the web server (GET or
  POST)
• ASPClient does the same but puts the values into
  the QueryString or the Form collection
• Not exactly what a browser usually does
• ASPClient must be able to catch the form
  submission
• With a little help from the DHTML object model

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Demo

• Invoke an ASP page with forms and utilize the
  information posted

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Topics to be covered

• Rationale and ASP infrastructure
• ASP client-side infrastructure
• Implementation details
• Globals and business components

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Working with Hyperlinks

• The browser resolves relative URLs using the
  current location
• The ASPClient browser defaults to its own folder
• Needs to redirect to the folder of the current
  ASP page

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Offline Detection

• Use the custom ServerVariables collection to let
  apps know when thery're working offline
• Also consider using the ScriptControl
• Use offline detection to
• Switch between (local) Access and (remote) SQL
  Server databases
• Local registry and remote LDAP server

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Custom ASP Objects

• The ScriptControl allows you to define
• Global variables
• Global functions
• They are injected into the global script
  namespace
• Visible to the global scope
• An enhanced version of VBScript

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What About ASP Components?

• ASP components may early-bind to the ASP type
  library
• They're needfully bound to the "real" ASP
• Dual ASP components should accept pointers to
  Response and Request
• Sacrificing early-binding, makes it possible to
  write components for dual pages

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Summary

• A customized browser
• Client-side ASP parser
• ScriptControl
• Automation objects which emulate ASP intrinsic
  objects
• ASP dual pages

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References

• MSDN Magazine
• Cutting Edge, September 2000
• "Infrastructure and Implementation of Response"
• Cutting Edge, October 2000
• "The Request Object and 3rd Party Components"
• MSDN Magazine
• July 1999
• Script Control
• Aug-Oct 1997
• Active Scripting interfaces

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• Questions?
• Dino Esposito
• Artis.Net
• desposito_at_artis.net