One of the
questions that most people ask when preparing for a Visual Basic 6.0 migration
to .NET has to do with the difficulty level of migrating an application to C#
compared to VB.NET.
Although the Visual Basic Upgrade Companion product can migrate VB6 code to both VB.NET
and C#, and both languages are first-class citizens in the .NET world, having
access to all the resources provided by the .NET Framework, there are some key
differences that will make a migration to C# demand more manual effort and
changes. The following are two of these differences:
- C# is
strictly typed as opposed to VB6 and there’s no way around it. Invoking a property or method
from an Object variable that is meant to be instantiated to a different
type at runtime would require a type-cast; otherwise the compiler will
throw an error. Therefore, many late-bound operations and unsafe
operations (such as assigning the value of a Long variable to an Integer
variable) that unfortunately were common in VB6, will generate compilation
errors. This will not happen in VB.NET unless you turn Option Strict on,
which is turned off by default.
- In C#,
only Structured Error Handling (“Try Catch”) is allowed. This means that any error-handling
code that could not be converted to “Try Catch” by VBUC will have to be
fixed manually, implying an important amount of manual work in some
projects (especially if statements such as “On Error Resume” and “On Error
Resume Next” are used in the VB6 code). On the other hand, VB.NET still
supports Unstructured Error Handling (“On Error GoTo”) for compatibility
with migrated applications, which will reduce the amount of manual work if
you are in a hurry. For VB.NET migrations, VBUC can disable the
conversion of “On Error GoTo” to “Try Catch” to speed up the migration
process and reduce manual changes.
Naturally,
strongly-typed and well-structured code is preferable. However, this increases
the amount of manual work that is needed to achieve Functional Equivalence.
More information on migrating Visual Basic 6.0 to C# can be found in the ArtinSoft
website:
http://www.artinsoft.com/vbc_csharpgen.aspx