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Visual Basic .NET

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Visual Basic .NET
Paradigm structured, imperative, object-oriented, declarative
Appeared in 2001 (last revised 2008)
Designed by Microsoft Corporation
Typing discipline dynamic, strong, both safe and unsafe[1], nominative
Major implementations .NET Framework, Mono
Dialects Microsoft Visual Studio .NET, .NET 2003, 2005, 2008

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.



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[edit] Versions of Visual Basic .NET

As of November 2007, there are four versions of Visual Basic .NET that were implemented by Visual Basic Team

[edit] Visual Basic .NET (VB 7)

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.[citation needed]

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.[citation needed]

[edit] Visual Basic .NET 2003 (VB 7.1)

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.

[edit] Visual Basic 2005 (VB 8.0)

Visual Basic 2005 is the name used to refer to the update to Visual Basic .NET, Microsoft having decided to drop the .NET portion of the title.

For this release, Microsoft added many features, including:

  • Edit and Continue – probably the biggest “missing feature” from Visual Basic .NET, 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 [2]
  • 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:

[edit] 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 [5] when it was found to be the subject of a Microsoft patent application [6] [7].

[edit] Visual Basic 2005 Express

Visual Basic 2005 Express - Microsoft's free development application.

Visual Basic 2005 Express – Microsoft‘s free development application.

As part of the Visual Studio product range, Microsoft created a set of free development environments for hobbyists and novices, the Visual Studio 2005 Express series. One edition in the series is Visual Basic 2005 Express Edition, which was succeeded by Visual Basic 2008 Express Edition in the 2008 edition of Visual Studio Express.[8]

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.

[edit] Visual Basic 2008 (VB 9.0)

Visual Basic 9.0 was released together with the Microsoft .NET Framework 3.5 on November 19, 2007.

For this release, Microsoft added many features, including:

[edit] Visual Basic ‘VBx’ (VB 10.0)

Visual Basic 10, also known as VBx, will offer support for the Dynamic Language Runtime. VB 10 is planned to be part of Silverlight 2.0.

[edit] Relation to older versions of Visual Basic (VB6 and previous)

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 that 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. Two important data type changes occurred with the move to VB.NET. Compared to VB6, the Integer data type has been doubled in length from 16 bits to 32 bits, and the Long data 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.[9]

[edit] Comparative samples

The following simple example demonstrates similarity in syntax between VB and VB.NET. Both examples pop up 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") 'MsgBox("Hello, World") can be used as well
End Sub
  • Note that all procedure calls must be made with parentheses in VB.NET, whereas in VB6 there were different conventions for functions (parentheses required) and subs (no parentheses allowed, unless called using the keyword Call).
  • 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.
  • Actually, there is a function called MsgBox in the Microsoft.VisualBasic namespace which can be used similarly to the corresponding function in VB6. There is, however, 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.VisualBasic namespace). 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 int (C#) or Integer (VB.NET) instead of System.Int32).

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 btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles btnClose.Click 
End Sub

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:

VB6 Example:

Private Sub Timer1_Timer()
    Me.Height = Me.Height - 1
End Sub

VB.NET example:

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Timer1.Tick
    Me.Height -= 1
End Sub

[edit] Criticism

Many long-time Visual Basic programmers have complained [10] about Visual Basic .NET because initial versions dropped a large number of language constructs and user interface features [11] 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.[12] On March 8, 2005, a petition [13] was set up in response to Microsoft’s refusal to extend its mainstream support [14] 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.[citation needed]

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.

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 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:

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

[edit] 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.[citation needed]

SharpDevelop provides an open-source alternative IDE. Like all .NET languages, programs written in VB.NET require the .NET framework to execute[citation needed].

[edit] Hello world example

The following is a very simple VB.NET program, a version of the classic “Hello world” example:

Public Class ExampleClass
        Public Shared Sub Main()
                System.Console.WriteLine("Hello, world!")
        End Sub
End Class

The effect is to write the text Hello, world! to the output console. Each line serves a specific purpose, as follows:

Public Class ExampleClass

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.

Public Shared Sub Main()

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.)

System.Console.WriteLine("Hello, world!")

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.

[edit] Notes

[edit] See also

[edit] External links

Wikibooks has a book on the topic of

[edit] Tutorials

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