VB6 Migration Strategies

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VB6 Migration Strategies

• Nick Page (Nick.Page_at_microsoft.com)
• Developer Platform Group
• Microsoft Ltd.

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Agenda

• Is Upgrading the best choice ?
• The Choices
• Migration Strategies
• Migration Tools
• FAQ
• COM
• VB.NET or C
• VB6 Support

3
Is Upgrading the best choice ?Evaluating your
application

• Business Value (to you, the ISV)
• Worthwhile investment to upgrade ?
• Uniqueness in the marketplace
• Could additional value be added through
  integration with other products which is
  difficult at the moment
• Does your application contain business rules not
  easily reproduced elsewhere
• How critical is the application to your
  customer's business ?

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Is Upgrading the best choice ? Evaluating your
application

• Application Quality (user and developer
  perspective)
• Ease of maintenance
• Agility
• Monolithic or componentised
• Consistency. Use of patterns.
• Current effectiveness. Need for workarounds,
  errors, level of support etc
• Stable application logic or likely to change?
• Good separation of business rules?
• Application Stability in development?
• Perception of users. Is it perceived as being
  dated ?

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Is Upgrading the best choice ? Evaluating your
application

• Application Quality (user and developer
  perspective)
• Type of application / project type / technologies
• Internet application making use of ActiveX
• DHTML
• Web Classes
• ActiveX control or ActiveX dll project
• Use of 3rd party ActiveX controls
• User Controls
• Multi-tier DNA application
• Use Visual Basic Upgrade assessment tool
• Skills
• Knowledge of existing solution
• Knowledge of .NET

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Is Upgrading the best choice ? Evaluating your
application
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The ChoicesMigrate

• Application is a good fit with business needs.
• Application needs only moderate functionality
  changes.
• A new application would require adding
  significant functionality to it, and it would
  need to be closely integrated with the existing
  application.

• High operational costs are associated with the
  existing application.
• Need to upgrade to .NET for strategic reasons.
• Future vision of the application includes Web
  services.
• Difficult and costly to find resources to
  maintain the existing application.

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The ChoicesRewrite

• The business rules are satisfactory but you will
  need to add additional functionality to the
  application.
• The available off-the-shelf solutions do not come
  close to meeting your needs.
• The existing application has poor quality code.
• The existing application has high maintenance
  costs.

• The time, cost, and disruption of rewriting the
  application are acceptable.

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The ChoicesReuse

• The business rules are satisfactory.
• The existing application has low operational
  costs.
• It is difficult to separate logic from persistent
  data and presentation layers.
• Only simple Web access is required, which allows
  you to use a wrapping solution

• You have sufficient resources to maintain core
  legacy code.
• Off-the-shelf software is central to the existing
  application, and it is possible to rely on
  third-party support and maintenance.

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The ChoicesReplace

• The existing application is significantly out of
  line with business needs.
• Making changes to the business model to fit an
  off-the-shelf solution is acceptable.
• The time, cost, and disruption of replacing the
  application are acceptable.

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Migration StrategiesInitial Learning

• Get some experience with .NET
• Look at .NET Application Architectures
• Proof of Concept
• Target a few, small applications
• Real World application
• Evaluate applications to find the most suitable
• Comparison can be made between upgraded and
  original
• Can be upgraded in modular fashion
• Plan for real application Migration

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Migration StrategiesPlanning for Migration

• Establish the scope of the project
• Measures for when application is functionally
  equivalent to original
• Other requirements
• Application Analysis
• Upgrade Assessment Tool
• Assess the target Architecture
• Avoid polluting a .NET architecture with non
  .NET technologies
• Write wrappers if necessary to avoid this
• Upgrade Strategy
• Complete Upgrade
• Staged Upgrade
• Vertical Slice / Horizontal Slice

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Migration StrategiesStages Upgrade
Presentation
Horizontal
Business
Vertical
Data
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MigrationTools

• Code Advisor
• Add-in for VB6
• Review code against pre-determined standards
• Identify migration issues
• Upgrade Assessment tool
• File Dependency and Call graphs
• Estimates of cost and effort to migrate
• Other potential migration issues

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MigrationMigration Wizard

• EXE DLL
• Copies project
• Creates reports
• Links to Help
• Four Levels
• Issue No Automatic Upgrade
• ToDo Requires Finishing
• Warning Possible Behavior Change
• Note Informational

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Tools
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MigrationThe Migration process

• Let the tools do most of the work
• Finish non-automated migration
• Reach a safe point through Functional Equivalence
• Evolve on top of the .NET Framework

Automated Tools
Functionally Equivalent
Current Application
Non automated changes
Preparation
Incremental Evolution
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FAQ DNA / COMShould we use COM / Enterprise
Services?

• .NET components can utilise Enterprise Services
• Services without Components registers
  automatically on first use.
• Start from position of not using ES
• Tight technology coupling
• deployment challenges
• DCOM ports
• DCOM proxy needs to be deployed
• What about Transaction Support?
• Few applications actually use Distributed
  Transactions. Most are local Transactions against
  a txn resource.
• Now have System.Transactions for doing local txns
• ASMX Web Services can initiate txns which can be
  distributed, although cannot flow txn context
  over web services to other components (as COM
  does)

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FAQ DNA / COMShould we use COM / Enterprise
Services?

• What about Loosely Coupled Events?
• There isnt a direct equivalent although there
  are patterns for delivering this capability over
  Web Services.
• Windows Communication Foundation will provide
  this capability.
• Object Pooling?
• Few scenarios where this should be used.
• Look first at ASMX Web Services, enhanced with
  WSE 3 where Security and Transactions are
  required.
• All the threading, initialisation etc is taken
  care of.
• Use Enterprise Services where
• you really need Distributed Transactions and need
  to flow txns across application boundaries.
• Are making real correct use of Loosely Coupled
  Events, Queued Components, Object Pooling

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FAQ VB.NET or CWhich language should we use?

• Both offer the full power of the .NET Framework
  and are excellent choices
• This is a choice both for VS2005 and going
  forward
• VB6 developers will feel more at home on VB 2005
• Developers looking for a tools-focused experience
  will feel more at home in VB
• Going with C can put a useful marker in the
  sand. No MS tools support for migration to C
  but there are 3rd party tools.
• Prescriptive guidance coming by end of the year.

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FAQ VB Support policyHow much longer are you
supporting VB6?

• Mainstream support ended March 31, 2005
• 7 years of free support is far longer than
  competitors
• Extended support is available through March 31,
  2008. Custom support through 2012
• The VB6 Runtime is slated to ship as a part of
  Windows Vista

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Resources

• Upgrading VB6 to VB.NET MS Press FREE !
• http//msdn.microsoft.com/vbrun/staythepath/additi
  onalresources/upgradingvb6/default.aspx
• Designing an Application Migration Strategy
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/dv_vstechart/html/appmigrationstrat
  .asp
• Upgrade Assessment tool and Upgrade guide
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/dnpag2/html/VB6ToVBNetUpgrade.asp
• Preparing your Visual Basic 6 Applications for
  Upgrade
• http//msdn.microsoft.com/vbasic/default.aspx?pull
  /library/en-us/dnvb600/html/vb6tovbdotnet.asp
• Code Advisor
• http//msdn.microsoft.com/vbasic/previous/2003/dow
  nloads/CodeAdvisor/

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Resources

• Visual Basic 6 Resource Centre
• http//msdn.microsoft.com/vbrun/
• .NET Patterns and Practices
• http//msdn.microsoft.com/practices/VS2005/
• Choosing a Distribution Technology today (inc
  COM/Enterprise Services)
• http//msdn.microsoft.com/webservices/choosing/def
  ault.aspx?pull/library/en-us/dnwebsrv/html/dsgpre
  scriptiveguidance.asp
• http//msdn.microsoft.com/webservices/choosing/
• System.Transactions
• http//msdn.microsoft.com/msdnmag/issues/05/12/tra
  nsactions/default.aspx
• ASP to ASP.NET Migration Wizard
• http//msdn.microsoft.com/asp.net/migration/aspmig
  /aspmigasst/default.aspx
• Online Training
• https//www.microsoftelearning.com/visualstudio200
  5/