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Methods of Migrating
The various methods that can be used to migrate the application
are given below. In many cases, these approaches will be combined.
A redesign from scratch may be better for some code modules whereas
many others might need only language/syntax level porting.
MigrationWizard
Visual Studio.NET provides a Visual Basic Upgrade Wizard (also called
as Migration Wizard). This wizard does almost the entire migration
barring some modifications that must be made to complete the upgrade
process.
Fresh Design
Redesign of certain core modules or perhaps the whole application
is a possible approach if new features of the .NET architectural
framework are considered. Managed code (under CLR) can run in tandem
with unmanaged code (e.g. COM components). Therefore it is possible
to reuse many existing components as such. However, paradigm shifts
towards XML web services, Web Forms, Windows Forms etc. call for
some rework in design, coding and deployment.
Use of Customized tools to enhance migration
Porting driven by a wizard and re-design are easier when migrated
using customized tools like the “Cal-Migrater” developed
internally by CSWL for a health care product migration. This tool
makes use of both the wizard and redesign approach to make faster
pace through the .NET porting activity.
Issues While Migrating
However there are a few issues that are to be taken care of while
migrating from VB to VB.NET. There are number of changes that can
be done to the VB6 application to make the upgrade process much
more efficient. Some important aspects are listed below.
Avoid using late binding. This is because properties and methods
cannot be verified during the upgrade process.
Specify default properties.
VB6 specifies
a default property for every component. For example, the default
of Textbox is Text property and Caption is default for Label component.
But in VB.NET there is nothing called as default property.
Use Zero-Bound
Array. In VB we can declare an array with any positive integer as
its lower bound. But in VB.NET all the arrays are zero bound.
Examine API
calls with fixed length strings in VB application because VB.NET
doesn't support fixed length strings.
Lines and
Shapes are not supported in VB.NET and hence cannot be upgraded.
Instead a graphic object is provided for shapes.
Re-Design
of the whole application can be considered if the application will
Grow over time. VB.NET being object oriented, the code can be reused
and the application can be extended with less effort and time. Doing
the same in VB6 would need a lot more time & effort.
Be taken online,
i.e. web application. VB.NET provides web forms that can be used
both for web application and VB application. This gives it dual
manageability.
Genie is migrating
all its technologies into the .NET platform. There are several reasons
and advantages for migrating existing applications to .NET.
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