Visual Basic .NET

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 VB and caused a rift within the developer community.

The great majority of VB.NET developers use Visual Studio .NET as their integrated development environment (IDE). SharpDevelop provides an open-source alternative IDE.

Like all .NET languages, programs written in VB.NET require the .NET framework to execute.

Versions of Visual Basic .NET

As of November 2005 there are three versions of Visual Basic .NET.

Visual Basic .NET

The original Visual Basic .NET was released alongside Visual C# and ASP.NET in 2002. C# — widely touted as Microsoft's answer to Java — received the lion's share of media attention, while VB.NET (sometimes known as VB7) was not widely covered. As a result, few outside the Visual Basic community paid much attention to it.

Those that 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 a greatly increased memory footprint.

Visual Basic .NET 2003

Visual Basic .NET 2003 was released with version 1.1 of the .NET Framework. New features included support for the .NET Compact Framework and a better VB upgrade wizard. Improvements were also made to the performance and reliability of the .NET IDE (particularly the background compiler) and runtime.

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.

Visual Basic 2005

Visual Basic 2005 is the next iteration of Visual Basic .NET, Microsoft having decided to drop the .NET portion of the title.

For this release, Microsoft added many features in an attempt to reintroduce some of the ease of use that Visual Basic is famous for — or infamous, with respect to "newbie" programmers — including:

Edit and Continue - probably the biggest "missing feature" from Visual Basic, allowing the modification of code and immediate resumption of execution
Design-time expression evaluation
The My pseudo-namespace (overview, details), which provides:
- easy access to certain areas of the .NET Framework that otherwise require significant code to access
- dynamically-generated classes (notably My.Forms)
Improvements to the VB-to-VB.NET converter
The Using keyword, simplifying the use of objects that require the Dispose pattern to free resources
Just My Code, which hides boilerplate code written by the Visual Studio .NET IDE
Data Source binding, easing database client/server development

The above functions (particularly My) are intended to reinforce Visual Basic .NET's focus as a rapid application development platform and further differentiate it from C#.

Visual Basic 2005 introduced features meant to fill in the gaps between itself and other "more powerful" .NET languages, adding:

.NET 2.0 languages features such as:
- generics ^*
- Partial classes, a method of defining some parts of a class in one file and then adding more definitions later; particularly useful for integrating user code with auto-generated code
XML comments that can be processed by tools like NDoc to produce "automatic" documentation
operator overloading ^*
Support for unsigned integer data types commonly used in other languages
Support for compound assignation operators such as "+=", "-=" which are present in many C-influenced programming languages

IsNot Patent

One other feature of Visual Basic 2005 is the conversion of 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.

Visual Basic 2005 Express

As part of the Visual Studio product range, Microsoft has created Visual Studio 2005 Express Editions for hobbyists and novices. One of these editions is Visual Basic 2005 Express Edition. The English edition is free to download from Microsoft. ^*

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 reasonable way to evaluate feasibility of conversion from older versions of Visual Basic.

Relation to Visual Basic

Whether Visual Basic .NET should be considered as just another version of Visual Basic or a completely different language is a topic of debate. This is not obvious, as once the methods that have been moved around and which can be automatically converted are accounted for, the basic syntax of the language has not seen many "breaking" changes, just additions to support new features like structured exception handling and short circuited expressions. One simple change that can be confusing to previous users is that of Integer and Long data types, which have each doubled in length; a 16-bit integer is known as a Short in VB.NET, while Integer and Long are 32 and 64 bits respectively. 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. Extensive documentation is available to cover changes in the syntax, debugging applications, deployment and terminology.

Comparative samples

The following simple example demonstrates similarity in syntax between VB and VB.NET. Both examples pops a message box saying "Hello, World" with an OK button.

Classic VB example:

Private Sub Command1_Click() MsgBox "Hello, World" End Sub

A VB.NET example:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click MessageBox.Show("Hello, World") End Sub

Note that all procedure calls must be made with parentheses in VB.NET, whereas these were only required for function calls (however in VB6 they could be used in procedure calls as well by using the Call keyword)
Also note that the names Command1 and Button1 are not obligatory. However, these are default names for a command button in VB6 and VB.NET respectively.

The following example demonstrates a difference between VB6 and VB.NET. Both examples unload the active window.

Classic VB Example: Private Sub cmdClose_Click() Unload Me End Sub

A VB.NET example: Private Sub cmdClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClose.Click Me.Close() End Sub

Controversy

Many long-time Visual Basic programmers have complained about Visual Basic .NET, because initial versions dropped a large number of language constructs and user interface features that were available in VB6 (which is now no longer sold), and changed the semantics of those that remained; for example, in VB.NET parameters are (by default) passed by value, not by reference. Detractors refer pejoratively to VB.NET as Visual Fred or DOTNOT. On March 8, 2005, a petition was set up in response to Microsoft's refusal to extend its mainstream support for VB6 at the end of that month.

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 Microsoft Intermediate Language, including VB.NET, compared to languages that compile to machine code.

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 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. Unfortunately, these functions are core to many business applications.

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 and Windows Server 2003. For other supported operating systems such as Windows XP, it must be separately installed. This has created much inconvenience to both programmers and users.

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:

completing common tasks in VB6, like creating a print preview
integrating VB6 and VB.NET solutions (dubbed VB Fusion)
converting VB6 code to VB.NET

Cross-platform and open-source development

The creation of open-source tools for VB.NET development have been slow compared to C#, although the Mono development platform provides an implementation of VB.NET-specific libraries and is working on a compiler, as well as the Windows Forms GUI library.

Notes

The actual version of first inclusion is not provided by official documentations, and is checked out by experiment. In version 2003, the most recent version before 2005, use of A += B will result in a compilation error and has to be replaced by A = A + B; while either piece of code will compile in version 2005.