Migrating ASP to ASP'NET

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Migrating ASP to ASP.NET
Pedro Miguel Rosa prosa_at_microsoft.com Senior
Software Engineer Developer Platform Group
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Agenda

• Classic Active Server Pages Background
• Why Migrate to ASP.NET?
• Migration Strategies
• ASP.NET Migration Issues
• Tools
• Questions

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Active Server Pages
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Active Server Pages

• Leading web app development platform
• Nearly 1 million developers using ASP today
• Many well known applications and sites
• Simple and approachable
• No compilers required just hit save
• Easy to use languages and object model
• Great integration with COM and COM
• Well established developer support base
• Online communities
• Books/Consulting/Conferences

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How it works.
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Internet Information Server
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Issues with Classic ASP

• Way too much code required
• Simple tasks often not easy
• Applications contain spaghetti code
• Poor reuse/encapsulation model
• Code runs from top of page to bottom
• Late-bound scripting, no strong typing
• Different language model in COM though
• Deployment issues
• COM and metabase

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Sample ASP Page
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How ASP.NET Works
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Requests
ASP.NET Http Runtime
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Migrating to ASP.NETBenefits of Migration

• Performance and scalability
• Strongly typed code, compiled into binaries
• Easily scalable to web farms
• Page, partial page, and data caching
• Productivity
• Web forms and server controls
• Web services
• Rich application framework
• Great tools and languages support
• Supports many mobile browsers

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Migrating to ASP.NETBenefits of Migration

• Security
• Can run under least privilege account
• Built-in forms based authentication
• Custom security infrastructure
• Reliability
• Application isolation, recycling, health
  detection
• Benefits of managed code
• Manageability
• XCOPY deployment
• Easily configurable (web.config)

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Migrating to ASP.NETThe Bad News

• Migration will always require work
• No magical migration tool
• Trivial pages may be easy
• Applications will be more difficult
• Reality is
• Cant simply change file extensions
• Incompatibilities in language, framework,
  environment

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Migrating to ASP.NETThe Good News

• Developers ASP skills will migrate
• Natural migration from VBScript to VB
• ASP intrinsic objects pulled forward
• Inline coding still possible
• Can leverage existing assets
• Existing pages can be converted
• Existing components still work (through interop)
• Migration can be incremental

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Migration Strategies

• Vertical Migration
• Use both ASP and ASP.NET
• Migrate individual features
• Horizontal Migration
• Move .asp files to .aspx
• Go for functional equivalence
• Re-write / New Application
• Move completely to ASP.NET
• Take advantage of new features

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Migration StrategiesVertical Migration

• ASP and ASP.NET pages run side by side
• Separately installed and configured
• Use ASP.NET without breaking ASP
• Migrate or add selected functionality
• Useful for new, isolated features
• Gain immediate perf benefits
• Limited interoperability
• ASP pages cant use ASP.NET features
• Run in separate worker processes
• No sharing of state

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Migration StrategiesHorizontal Migration

• Rename .asp to .aspx, and correct problems
• Correct page syntax
• Translate VBScript to Visual Basic .NET
• Take advantage of key ASP.NET features
• Can call Framework code
• Page compilation
• Scalable session state, caching
• Not a full port yet
• No improvements in code manageability
• COM interop work may be needed

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Migration StrategiesFull Rewrite

• Complete rewrite of pages and components
• Use ASP.NET server controls
• Rewrite business components using Framework
• Take full advantage of ASP.NET
• True code separation, encapsulation
• Page framework and controls
• ASP.NET Security

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Migration StrategiesGuidelines Summary

• Use vertical migration for
• Well partitioned applications
• New functionality in existing apps
• Use horizontal migration for
• Heavy use of application or session state
• Complex, unfactorable tiers
• Use rewrite for
• Re-architecture of system
• Significant new functionality

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ASP.NET Migration Issues
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Semantic ChangesProgramming Language

• Single choice of server language
• Cannot mix languages on page
• Client script not affected
• VBScript ? Visual Basic .NET
• All variables have a specific type
• No more default properties (big change)
• No Set and Let syntax
• Parentheses required for calling subroutines
• Arguments now ByVal by default

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Code Changes

• Page functions
• Must be in ltscript runatservergt blocks
• Page render functions
• Not supported, must use Response.Write
• Variable references
• Cannot reference variables in other lt gt blocks
• Page directives (_at_Option, _at_Session, etc.) no
  longer supported
• Merged into single Page directive

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Server ComponentsOptions for Using COM Objects

• Simple Usage
• Call Server.CreateObject(progid) and access it
  as a late-bound object
• Create .NET wrapper classes
• Provides early binding
• Optimizes performance of calls
• TLBIMP.exe utility
• Rewrite using .NET

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Server ComponentsUsing ASP Intrinsics in
components

• Support for ASP intrinsics
• ObjectContext intrinsic Flow
• Application OnStart and OnEnd
• ASPCompat mode
• lt_at_ page aspcompattrue gt
• Enables access to intrinsic objects

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ASP.NET Migration Examples
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Server ComponentsPerformance Considerations

• Marshalling costs
• Calls between ASP.NET and COM
• Performance benefits by rewriting COM in .NET
• ASP.NET Thread Pool now MTA -- not STA
• What is an MTA? What is an STA?
• Impacts performance of apartment components
• VB5 and VB6 Apartment Components
• Can enable STA Thread Pool on a per-page basis
• Address perf. of existing VB components
• lt_at_ Page ASPCompattrue gt
• Not necessary for C MTA components

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Security Changes

• ASP Use Windows (IIS) authentication
• NTLM (default), Basic, Digest, or Kerberos
• Impersonate caller by default
• Forms based auth roll your own
• ACL based URL authorization
• ASP.NET Customizable authentication
• Windows (default), Forms, or Passport
• Impersonation must be enabled
• Built-in forms authentication
• Role based declarative authorization

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Configuration Changes

• ASP Configuration
• Binary data store used by IIS (metabase)
• Used by Classic ASP
• Changes required local server access
• ASP.NET XML Configuration
• Machine.config, web.config
• Most IIS settings do not affect ASP.NET
• Changes do not require local server access

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Tools
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ASP.NET Migration Assistant

• Features
• Corrects ASP.NET page syntax
• Translates VBScript into Visual Basic .NET
• Visual Studio or command line translation
• Starting point for further migration
• Available from
• http//www.asp.net/migrationassistants/

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ASP.NET Migration Assistant
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Summary

• Migration not seamless
• Will involve some work
• Can be done incrementally
• Worth the efforts
• Better performance
• Easier development
• Cleaner and more manageable code
• Platform to build apps for the future

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