Advanced ASP 'Net 2'0

1
Advanced ASP .Net 2.0

• Gerald Walsh
• GT Data Systems
• MCSD, MCAD, MCT, MVP

2
Agenda

• Writing custom HTTP handlers
• Creating Asynchronous ASP.Net Pages

3
ASP.Net Request Processing
ASPNET_WP.EXE
Request is passed to the ASP.Net ISAPI
Interface ASPNET_ISAPI.dll via Named Pipe
HTTP Pipeline
HTTP Request
Web.config
HTTP Response
IIS 6.0 Server ISAPI Processes Request INETINFO.EX
E or DLLHOST.EXE
HTML Response Is returned back through the
ASP.Net pipeline.
ASP.Net HTTP Handler Code
4
the HTTP pipeline

• Foundation for ASP.NET pages Web Services
• General-purpose framework for server-side HTTP
  programming

Pipeline Classes
Context Classes
5
Writing Custom HTTP Handlers

• ASP.Net is based on processing custom handlers.
• It provides several well known built-in handlers
• Page
• Web Service
• .Net Remoting
• Building Custom Handlers allow you to develop
  your own processes in addition to these.
• Custom handlers can offer much greater
  performance than using pages and can process
  requests in custom non-standard ways.
• Implemented as a separate assembly or as an ASHX
  file.

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The IHttpHandler Interface

• Imports System
• Imports System.Web
• Public Class Handler Implements IHttpHandler
• Public Sub ProcessRequest(ByVal context As
  HttpContext) Implements _ IHttpHandler.ProcessRequ
  est
• Code here to process request using
  context object
• End Sub
• Public ReadOnly Property IsReusable() As
  Boolean Implements _ IHttpHandler.IsReusable
• Get
• Return True
• End Get
• End Property
• End Class

7
Registering Your Handler

• Edit Web.config
• ltconfigurationgt
• ltsystem.webgt
• lthttpHandlersgt
• ltadd verb path.hdlr
• typeMyNamespace.MyHandlerClass, assembly
• validatefalse/gt
• lt/httpHandlersgt
• lt/system.webgt
• lt/configurationgt

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Registering Your Handler in IIS6

• Register your custom file extension in the IIS
  Metabase.
• Web Application Properties ?
• Configuration ?
• Mappings
• Executable Path set to aspnet_isapi.dll

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Registering Handlers in IIS7
10
Registering Handlers in IIS7
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Alternate Method

• Add a ASHX resource to your project
• Includes a special directive
• lt_at_ WebHandler LanguageVB ClassNamespace.MyHa
  ndler gt
• The handler will run automatically when invoked,
  no registration or deployment is necessary.
• The registration is actually handled by another
  built-in handler.
• Quick Tip Add a CodeBehind attribute to the
  WebHandler directive to use intellisense and
  other code editor capabilities.

12
DEMO

• Building a simple HTTP Handler

13
Asynchronous Pages

• By default ASP.Net pages execute synchronously.
• When IIS is serving a large number of requests it
  can run out of available threads.
• IIS then returns a 503 Server Too Busy
  response.
• Async requests improve web server performance by
  reducing thread contention in the ASP.Net process
  request thread pool.
• By default ASP.Net request queue holds a maximum
  of 100 threads.
• appRequestQueueLimit can be set up to 5000

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The Page Async Attribute

• lt_at_ Page Asynctrue . . . gt
• Causes the page parser to generate the
  IHttpAsyncHandler interface in the dynamically
  generated class.
• This then allows for asynchronous handlers to be
  registered for the PreRenderComplete event.

15
IHttpAsyncHandler

• A standard Async processing design pattern that
  Implements two methods
• BeginProcessRequest(HttpContext, callback,
  object)
• EndProcessRequest(IAsyncResult)

16
AddOnPreRenderCompleteAsync

• Handles registration of asynchronous event
  handlers to execute during the pages
  PreRenderComplete event.
• AddOnPreRenderCompleteAsync(
• new BeginEventHandler(BeginProc),
• new EndEventHandler(EndProc)
• )

17
Uses for Async Pages

• Long Running or Slow Database Operations.
• Calling Web Services.
• Fire and Forget Web Page Requests.

18
DEMO

• Building an Asynchronous ASPX Page

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Resources

• Gerald_at_GTDataSystems.com
• Book Programming Microsoft ASP.NET 2.0
  APPLICATIONS Advanced Topics by Dino Esposito,
  Microsoft Press.
• http//www.ASP.Net
• http//msdn.microsoft.com
• http//msdn.microsoft.com/msdnmag/issues/02/09/htt
  ppipelines/

20
The ASP.net Cache Object

• A hashtable used to store frequently accessed
  data.
• Global to the application.
• Similar to the Application object but has
  additional management functionality.
• Dependency Functionality
• Sliding and Fixed Expiration of Data
• Prioritization of data in cache

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Cache.Add

• Cache.Add(
• Key as string,
• Value as object,
• Dependencies as CacheDependency,
• AbsoluteExpiration as Date,
• SlidingExpiration as timespan,
• Priority as CacheItemPriority,
• onRemovedCallback as CacheItemRemovedCallback
• )

22
Cache Dependencies

• CacheDependency Object
• Can Be
• File
• Directory
• SQL Server Data Dependency
• Custom Dependency
• Can be bound to multiple cache items
• Cache.Insert(Key, Value, Dependency)

23
SQL Cache Dependency

• Supported on SQL 7.0 and later
• Managed with the SqlCacheDependencyAdmin object
• SQL Must first be configured to support
  dependencies.
• Use aspnet_regsql.exe d ltdbnamegt or
  EnableNotifications method in code.

24
SQL Cache Dependency

• Creates a table in the DB to track data changes
  in enabled tables. AspNet_SqlCacheTablesForChangeN
  otification
• Call to EnableTableForNotifications adds triggers
  and table entry to track changes.
• SqlCacheDependency object periodically queries
  the table to check for data changes.

25
DEMO

• Using the Cache Object