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), which is implemented on the .NET Framework. Microsoft currently supplies two major implementations of Visual Basic: Microsoft Visual Studio 2010, which is commercial software and Visual Basic Express Edition 2010, which is free of charge.

Software and Hardware Requirements

Software Requirements

Visual Studio 2010 can be installed on the following operating systems:

• Windows XP (x86) with Service Pack 3 - all editions except Starter Edition
• Windows Vista (x86 & x64) with Service Pack 2 - all editions except Starter Edition
• Windows 7 (x86 & x64)
• Windows Server 2003 (x86 & x64) with Service Pack 2
• Windows Server 2003 R2 (x86 & x64)
• Windows Server 2008 (x86 & x64) with Service Pack 2
• Windows Server 2008 R2 (x64)

Supported Architectures:

• 32-Bit (x86)
• 64-Bit (x64)

Hardware Requirements

• Computer that has a 1.6GHz or faster processor
• 1 GB (32 Bit) or 2 GB (64 Bit) RAM (Add 512 MB if running in a virtual machine)
• 3GB of available hard disk space
• DirectX 9 capable video card running at 1024 x 768 or higher-resolution display
• DVD-ROM Drive

Versions

There are 5 versions of Visual Basic .NET implemented by the Visual Basic Team.

Visual Basic .NET (2002) (VB 7.0)

First version of Visual Basic .NET, which run 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 is the name used to refer to the 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
• 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 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 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^[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]

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 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.

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

A VB.NET example, MsgBox or the MessageBox class can be used:

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
Button1.Click
        Msgbox("Hello, World")
    End Sub
End Class

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
Button1.Click
        MessageBox.Show("Hello, World")
    End Sub
End Class

• Both Visual Basic 6 and Visual Basic .NET will 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.

Classic VB Example:

Sub cmdClose_Click()
    Unload Me
End Sub

A VB.NET example:

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 Example:

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

VB.NET example:

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

Criticism

Long-time Visual Basic users 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 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] On 8 March 2005, a petition^[13] was set up in response to Microsoft's refusal to extend its mainstream support^[14] for VB6.

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 to respond 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.

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. This problem also exists on early versions of Visual Basic (prior to VB5), which could not compile to native 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 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. 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 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 have 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,^[15] 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.^[16]
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.^[17] 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).^[18]

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
• Comparison of programming languages

References

Further reading

External links

• Visual Basic Developer Center
• Microsoft Visual Basic Express
• The Visual Basic Team Blog
• VB.NET tutorials
• Visual Basic 2008 programming