Visual Basic .NET

Visual Basic .NET

Paradigm(s)	Structured, imperative, object-oriented and declarative
Appeared in	2001
Designed by	Microsoft
Developer	Microsoft
Stable release	2012 (11.0.0.0) (15 August 2012; 7 months ago (2012-August-15))
Typing discipline	Static, strong, both safe and unsafe,[1] nominative
Major implementations	Microsoft Visual Studio, Microsoft Visual Studio Express, SharpDevelop, .NET Framework SDK and Mono
Dialects	Microsoft Visual Basic
Influenced by	.NET Framework
Platform	CLR
OS	Chiefly Microsoft Windows Also on Android, BSD, iOS, Linux, Mac OS X, Solaris and Unix
License	Proprietary software (Commercial software or freeware)
Usual filename extensions	.vb and .vbs
msdn.microsoft.com/en-us/vstudio/hh38 8573

Microsoft Visual Basic 2010 Express, an integrated development environment that implements Visual Basic .NET.

Visual Basic .NET (VB.NET) is an object-oriented computer programming language that can be viewed as an evolution of the classic Visual Basic (VB), implemented on the .NET Framework. Microsoft currently supplies two main editions of IDEs for developing in Visual Basic: Microsoft Visual Studio 2012, which is commercial software and Visual Basic Express Edition 2012, which is free of charge. The command-line compiler, VBC.EXE, is installed as part of the freeware .NET Framework SDK. Mono also includes a command-line VB.NET compiler. The most recent version is VB 2012, which was released on August 15, 2012.

Versions

There are 6 versions of Visual Basic .NET implemented by the Visual Basic team.

Visual Basic .NET (2002) (VB 7.0)

The first version of Visual Basic .NET, which runs on .NET framework 1.0. The most important feature is Managed code, which contrasts with Visual Basic 6.0 and before.

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 available in the Visual Studio.NET Academic Edition (VS03AE). VS03AE is distributed to a certain number of scholars from each country without cost.

Visual Basic 2005 (VB 8.0)

Visual Basic 2005 was the name used to refer to Visual Basic .NET, as Microsoft decided to drop the .NET portion of the title.

For this release, Microsoft added many features, including:

• Edit and Continue
• Design-time expression evaluation.
• The My pseudo-namespace (overview, details), which provides:sindhu
  • 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 when debugging hides (steps over) boilerplate code written by the Visual Studio .NET IDE and system library code
• 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 bridge the gaps between itself and other "more powerful" .NET languages, adding:

• Features of other .NET 2.0 languages 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^[4]
• Support for unsigned integer data types commonly used in other languages

'IsNot' Operator Patent Application

One other feature of Visual Basic 2005 is the IsNot operator that makes 'If X IsNot Y' equivalent to 'If Not X Is Y', which gained notoriety^[5] when it was found to be the subject of a Microsoft patent application.^[6][7]

Visual Basic 2008 (VB 9.0)

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

For this release, Microsoft added many features, including:

• A true conditional operator, "If(condition as boolean, truepart, falsepart)", to replace the "IIf" function.
• Anonymous types
• Support for LINQ
• Lambda expressions
• XML Literals
• Type Inference
• Extension methods

Visual Basic 2010 (VB 10.0)

In April 2010, Microsoft released Visual Basic 2010. Microsoft had planned to use the Dynamic Language Runtime (DLR) for that release^[8] but shifted to a co-evolution strategy between Visual Basic and sister language C# to bring both languages into closer parity with one another. Visual Basic's innate ability to interact dynamically with CLR and COM objects has been enhanced to work with dynamic languages built on the DLR such as IronPython and IronRuby.^[9] The Visual Basic compiler was improved to infer line continuation in a set of common contexts, in many cases removing the need for the "_" line continuation character. Also, existing support of inline Functions was complemented with support for inline Subs as well as multi-line versions of both Sub and Function lambdas.^[10]

Visual Basic 2012 (VB 11.0)

The latest version of Visual Basic .NET, which runs on .NET framework 4.5. Async Feature, Iterators, Call Hierarchy, Caller Information and Global Keyword in Namespace Statements are some of the major features introduced in this version of VB.

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 version numbers used for the new Visual Basic (7, 7.1, 8, 9, ...) clearly imply that it is viewed by Microsoft as still essentially the same product as the old Visual Basic.

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.^[11]

Comparative examples

The following simple examples compare VB and VB.NET syntax. Each example creates a "Hello, World" message box with an OK button.

VB6:

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

VB.NET (MsgBox or MessageBox class can be used):

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) HandlesButton1.Click MessageBox.Show("Hello, World")End Sub

• Both Visual Basic 6 and Visual Basic .NET automatically generate the Sub and End Sub statements when the corresponding button is clicked in design view. Visual Basic .NET will also generate the necessary Class and End Class statements. The developer need only add the statement to display the "Hello, World" message box.
• 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).
• The names Command1 and Button1 are not obligatory. However, these are default names for a command button in VB6 and VB.NET respectively.
• In VB.NET, the Handles keyword is used to make the sub Button1_Click a handler for the Click event of the object Button1. In VB6, event handler subs must have a specific name consisting of the object's name ("Command1"), an underscore ("_"), and the event's name ("Click", hence "Command1_Click").
• There is a function called MsgBox in the Microsoft.VisualBasic namespace 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.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).
• In VB 2008, the inclusion of ByVal sender as Object, ByVal e as EventArgs has become optional.

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

VB6:

Sub cmdClose_Click() Unload MeEnd Sub

VB.NET:

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

The 'cmd' prefix is replaced by the 'btn' prefix, conforming to the new convention previously mentioned.

Visual Basic 6 did not provide common operator shortcuts. The following are equivalent:

VB6:

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

VB.NET:

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

Criticism

When first introduced, many long-time Visual Basic users complained about Visual Basic .NET because initial versions dropped a large number of language constructs and user interface features that were part of VB6 (which is no longer sold by Microsoft), 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] One major complaint was that "edit-and-continue", the ability to fix bugs by changing source code in a running program when it is paused at a breakpoint and continue running the code, had been eliminated: this feature was a major productivity aid that had attracted many developers to VB6.

Many of the changes were necessary because they needed to reflect differences between Windows Foundation Classes and equivalent classes in the .NET framework (e.g., for user-interface controls): in addition, certain changed features, such as restricting the scope of local variables to the block where they were declared, and passing parameters by value (which is the only means permitted in Java) make code less error-prone. Reduced risk of error was also the justification for removing features such as computed gosub/goto and the elimination of line numbers (both a legacy of the BASIC language's FORTRAN heritage.) In general, the idea was to make the .NET libraries, rather than language-specific libraries, perform most of the work, so that code written either in VB.NET or C Sharp would compile to almost identical intermediate-code.

However, many of these semantic changes were not backward-compatible with much existing code, and existing code required rewriting and testing, a significant expense when the body of code was non-trivial in size. As author Joel Spolsky noted, "It was the first time a Microsoft upgrade did not respect the work that users did using the previous version of a product." ^[13]

Microsoft's IDE, Visual Studio, did support some degree of automatic translation to VB.NET when VB6 code was pasted into Visual Studio. Also, the VB.NET compiler reported multiple errors (up to a user-specified threshold - e.g., 100 errors) all at once instead of one at a time, with fixes to the source reducing the error list through a process of background compilation. Despite this, adoption of VB.NET was still delayed until 2005, when Microsoft finally reintroduced edit-and-continue: this feature was also made available to C sharp developers.

It is simpler to decompile languages that target Common Intermediate Language (CIL), including VB.NET, compared to languages that compile to machine code. Tools such as .NET Reflector can provide a close approximation to the original code due to the large amount of metadata provided in CIL.^{[citation needed]} This is also true of early versions of Visual Basic (prior to VB5), which could not compile to native code.

Visual Basic 6.0 programs that are mainly algorithmic in nature can be migrated with few difficulties, but certain types of code are more troublesome, namely :

• Database support: .NET's framework for database access, ADO.NET, emphasizes disconnected operations, which use database-server resources as economically as possible by releasing them when not in use. This results in more scalable code than if the older Data Access Objects or ActiveX Data Objects were used, but the code is also more complex.
• Graphics: .NET has new (and more powerful) libraries for graphics.
• Unmanaged operations: .NET, like Java, emphasizes security, so unmanaged code is used only as a last resort.

Other syntactical differences relate to changes made to bring VB.Net into alignment with other .Net languages, such as zero-based arrays (all .Net arrays are 0 to n-1 subscript, whereas classic VB arrays were one-based by default, 1 to n subscript), and structured exception handling (classic VB used a proprietary ON ERROR mechanism); such changes can be difficult or impossible to convert automatically, and converters typically flag such problem areas for manual conversion.

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 7, 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 focused around making it easier to move new development and shift existing codebases from VB6 to VB.NET. An offering in 2005 was the VBRun website, offering code samples and articles for:

• Using VB.NET to complete tasks that were common in VB6, like creating a print preview
• Integrating VB6 and VB.NET solutions (dubbed VB Fusion)

Cross-platform and open-source development

The creation of open-source tools for VB.NET development has been slow compared to C#, although the Mono development platform provides an implementation of VB.NET-specific libraries and a VB.NET 8.0 compatible compiler written in VB.NET,^[14] as well as standard framework libraries such as Windows Forms GUI library.

SharpDevelop and MonoDevelop are open-source alternative IDEs.

Examples

The following is a very simple VB.NET program, a version of the classic "Hello world" example created as a console application:

Module Module1 Sub Main() Console.WriteLine("Hello, world!") End Sub End Module

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

Module Module1

This is a module definition, a division of code similar to a class, although modules can contain classes. Modules serve as containers of code that can be referenced from other parts of a program.^[15]
It is common practice for a module and the code file, which contains it, to have the same name; however, this is not required, as a single code file may contain more than one module and/or class definition.

Sub Main()

This is the entry point where the program begins execution.^[16] Sub is an abbreviation of "subroutine."

Console.WriteLine("Hello, world!")

This line performs the actual task of writing the output. Console is a system object, representing a command-line interface and granting programmatic access to the operating system's standard streams. The program calls the Console method WriteLine, which causes the string passed to it to be displayed on the console. Another common method is using MsgBox (a Message Box).^[17]

This piece of code is a solution to Floyd's Triangle:

Imports System.Console Module Program Sub Main() Dim rows As Integer ' Input validation. Do Until Integer.TryParse(ReadLine("Enter a value for how many rows to be displayed: "),rows) AndAlso rows >= 1 WriteLine("Allowed range is 1 and {0}", Integer.MaxValue) Loop ' Output of Floyd's Triangle Dim current = 1 For row = 1 To rows For column = 1 To row Write("{0,-2} ", current) current += 1 Next WriteLine() Next End Sub ''' <summary> ''' Shadows Console.ReadLine with a version which takes a prompt string. ''' </summary>  Function ReadLine(Optional prompt As String = Nothing) As String If prompt IsNot Nothing Then Write(prompt) End If Return Console.ReadLine() End Function  End Module

See also

• Microsoft Visual Studio Express
• Comparison of C# and Visual Basic .NET
• Visual Basic for Applications
• Microsoft Small Basic
• Comparison of programming languages

References

Further reading

External links

• Visual Basic Developer Center
• Microsoft Visual Basic Express
• The Visual Basic Team Blog
• Visual Basic Tutorials