Thursday, April 5, 2007

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.
1 Versions of Visual Basic .NET
1.1 Visual Basic .NET
1.2 Visual Basic .NET 2003
1.3 Visual Basic 2005
1.3.1 IsNot Patent
1.3.2 Visual Basic 2005 Express
2 Relation to Visual Basic
2.1 Comparative samples
2.2 Controversy
3 Cross-platform and open-source development
4 Hello World Example
5 See also
6 Notes
7 External links
7.1 Tutorials

[edit] Versions of Visual Basic .NET
As of November 2006 there are three versions of Visual Basic .NET.

[edit] 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.[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
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
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, 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 [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:
.NET 2.0 languages features such as:
generics [3]
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
Nullable Types
XML comments that can be processed by tools like NDoc to produce "automatic" documentation
operator overloading [4]
Support for unsigned integer data types commonly used in other languages

[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]

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.

[edit] 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.
Actually, there is a function called MsgBox in the Microsoft.VisualBasic namespace, but the System.Windows.Forms.MessageBox class is a preferred way of displaying message boxes since it has more features and is less language-specific.
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()
Form1.Height = Form1.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] Controversy
Many long-time Visual Basic programmers have complained [8] about Visual Basic .NET, because initial versions dropped a large number of language constructs and user interface features [9] 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.[10] On March 8, 2005, a petition [11] was set up in response to Microsoft's refusal to extend its mainstream support [12] 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 Microsoft 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 MSIL.
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.
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, 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)
converting VB6 code to VB.NET

[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]

[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.

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