Visual Basic .NET (VB.NET) is an object-oriented computer language that can be viewed as an evolution of Microsoft's Visual Basic (VB) implemented on the Microsoft .NET framework. Its introduction has been controversial, as significant changes were made that broke backward compatibility with older versions and caused a rift within the developer community.
Those who did try the first version found a powerful but very different language under the hood, with disadvantages in some areas, including a runtime that was ten times as large to package as the VB6 runtime and an increased memory footprint.
In addition, Visual Basic .NET 2003 was also available in the Visual Studio .NET 2003 Academic Edition (VS03AE). VS03AE is distributed to a certain number of scholars from each country for free.
For this release, Microsoft added many features, including:
Visual Basic 2005 introduced features meant to fill in the gaps between itself and other "more powerful" .NET languages, adding:
'If Not X Is Y'to
'If X IsNot Y'which gained notoriety when it was found to be the subject of a Microsoft patent application .
The Express Editions are targeted specifically for people learning a language. They have a streamlined version of the user interface, and lack more advanced features of the standard versions. On the other hand, Visual Basic 2005 Express Edition does contain the Visual Basic 6.0 converter, so it is a way to evaluate feasibility of conversion from older versions of Visual Basic.
For this release, Microsoft added many features, including:
Integerdata type has been doubled in length from 16 bits to 32 bits, and the
Longdata type has been doubled in length from 32 bits to 64 bits. This is true for all versions of VB.NET. A 16-bit integer in all versions of VB.NET is now known as a
Short. Similarly, the Windows Forms GUI editor is very similar in style and function to the Visual Basic form editor.
The things that have changed significantly are the semantics — from those of an object-based programming language running on a deterministic, reference-counted engine based on COM to a fully object-oriented language backed by the .NET Framework, which consists of a combination of the Common Language Runtime (a virtual machine using generational garbage collection and a just-in-time compilation engine) and a far larger class library. The increased breadth of the latter is also a problem that VB developers have to deal with when coming to the language, although this is somewhat addressed by the My feature in Visual Studio 2005.
The changes have altered many underlying assumptions about the "right" thing to do with respect to performance and maintainability. Some functions and libraries no longer exist; others are available, but not as efficient as the "native" .NET alternatives. Even if they compile, most converted VB6 applications will require some level of refactoring to take full advantage of the new language. Documentation is available to cover changes in the syntax, debugging applications, deployment and terminology.
Classic VB example:
A VB.NET example:
Button1are not obligatory. However, these are default names for a command button in VB6 and VB.NET respectively.
Microsoft.VisualBasicnamespace which can be used similarly to the corresponding function in VB6. There is a controversy about which function to use as a best practice (not only restricted to showing message boxes but also regarding other features of the
Microsoft.VisualBasicnamespace). Some programmers prefer to do things "the .NET way", since the Framework classes have more features and are less language-specific. Others argue that using language-specific features makes code more readable (for example, using
Integer(VB.NET) instead of
The following example demonstrates a difference between VB6 and VB.NET. Both examples unload the active window.
Classic VB Example:
A VB.NET example:
Note the 'cmd' prefix being replaced with the 'btn' prefix, conforming to the new convention previously mentioned.
Visual Basic 6 did not provide common operator shortcuts. The following are equivalent:
VB.NET's supporters state that the new language is in most respects more powerful than the original, incorporating modern object oriented programming paradigms in a more natural, coherent and complete manner than was possible with earlier versions. Opponents tend not to disagree with this, instead taking the position that although VB6 has flaws in its object model, the cost in terms of redevelopment effort is too high for any benefits that might be gained by converting to VB.NET. Independent developers producing software for Internet distribution have also taken issue with the size of the runtime.
It is simpler to decompile languages that target Common Intermediate Language, including VB.NET, compared to languages that compile to machine code. Tools like .NET Reflector can provide a close approximation to the original code due to the large amount of metadata provided in CIL.
Microsoft supplies an automated VB6-to-VB.NET converter with Visual Studio .NET, which has improved over time, but it cannot convert all code, and almost all non-trivial programs will need some manual effort to compile. Most will need a significant level of code refactoring to work optimally. Visual Basic programs that are mainly algorithmic in nature can be migrated with few difficulties; those that rely heavily on such features as database support, graphics, unmanaged operations or on implementation details are more troublesome.
However in 2005 ArtinSoft, the company that developed the VB6-to-VB.NET converter for Microsoft that comes with Visual Studio .NET, developed a migration tool called the ArtinSoft Visual Basic Upgrade Companion. This tool expands upon the migration wizard included in Visual Studio .NET by providing some automated code refactoring, such as type inference for late-bound variables—producing explicitly typed variables—and conversion to structured error handling, among many other tweaks that improve code quality.
Using artificial intelligence algorithms, it is possible for this new tool to recognize certain code patterns that can be reorganized into more structured versions, potentially yielding a higher quality .NET code. For example, the tool is able to automatically recognize commonly used patterns of “
On Error GoTo”, analyze them, and convert them to code blocks that use “
Try ... Catch” instead of the legacy error handling model—in many cases with no human intervention. However, a line-by-line conversion will not be able to create the object-oriented style of programming that is at the heart of .NET programming. Other tools such as NewCode's use a model-driven approach to enable users to re-engineer the application structure on a model, prior to .NET code generation.
In addition, the required runtime libraries for VB6 programs are provided with Windows 98 SE and above, while VB.NET programs require the installation of the significantly larger .NET Framework. The framework is included with Windows Vista, Windows XP Media Center Edition, Windows XP Tablet PC Edition, Windows Server 2008 and Windows Server 2003. For other supported operating systems such as Windows 2000 or Windows XP (Home or Professional Editions), it must be separately installed.
Microsoft's response to developer dissatisfaction has focused around making it easier to move new development and shift existing codebases from VB6 to VB.NET. Their latest offering is the VBRun website, which offers code samples and articles for:
The effect is to write the text Hello, world! to the output console. Each line serves a specific purpose, as follows:
This is a class definition. It is public, meaning objects in other projects can freely use this class. All the information between this and the following
End Class describes this class.
This is the entry point where the program begins execution. It could be called from other code using the syntax
ExampleClass.Main(). (The Public Shared portion is a subject for a slightly more advanced discussion.)
This line performs the actual task of writing the output. Console is a system object, representing a command-line console where a program can input and output text. The program calls the Console method WriteLine, which causes the string passed to it to be displayed on the console.