What's New in the Visual Basic Language for Visual Basic 6.0 Users
Visual Basic 2008 has many new and improved language features—such as inheritance, interfaces, and overloading—making it a powerful object-oriented programming language. This page highlights some of the biggest changes and provides links to in-depth information.
If you are familiar with Visual Basic 6.0, see Language Changes for Visual Basic 6.0 Users for an introduction to the new concepts.
For a hands-on introduction to new language features in Visual Basic 2008, see Visual Basic Guided Tour.
The following are new language features in Visual Basic 2008.
Visual Basic 2008 supports inheritance by allowing you to define classes that serve as the basis for derived classes. Derived classes inherit and can extend on the properties and methods of the base class. They can also override inherited methods with new implementations of the base class. All classes created with Visual Basic 2008 are inheritable by default. Because the forms you design are really classes, you can use inheritance to define new forms based on existing ones. For details, see Inheritance in Visual Basic.
Visual Basic 2008 supports structured exception handling, using an enhanced version of the Try...Catch...Finally syntax supported by other languages such as C++. Structured exception handling combines a modern control structure (similar to Select Case or While) with exceptions, protected blocks of code, and filters. Structured exception handling makes it easy to create and maintain programs with robust, comprehensive error handlers. For details, see Introduction to Exception Handling.
Overloading is the ability to define properties, methods, procedures, or operators that have the same name but use different data types. You can use overloaded procedures to provide as many implementations as necessary to handle different kinds of data, while giving the appearance of a single, versatile procedure. For details, see Overloaded Properties and Methods.
Overriding Properties and Methods
The Overrides keyword allows derived objects to override characteristics inherited from parent objects. Overridden members have the same arguments as the members inherited from the base class, but they have different implementations. A member's new implementation can call the original implementation in the parent class by preceding the member name with MyBase. For details, see Overriding Properties and Methods.
Constructors and Destructors
Constructors are procedures that control initialization of new instances of a class. Conversely, destructors are methods that free system resources when a class leaves scope or is set to Nothing. Visual Basic 2008 supports constructors and destructors using the Sub New and Sub Finalize procedures. For details, see Object Lifetime: How Objects Are Created and Destroyed.
Visual Basic 2008 introduces three new data types. The Char data type is an unsigned 16-bit quantity used to store Unicode characters. It is equivalent to the .NET Framework System.Char data type. The Short data type, a signed 16-bit integer, was named Integer in earlier versions of Visual Basic. The Decimal data type is a 96-bit signed integer scaled by a variable power of 10. In earlier versions of Visual Basic, it was available only within a Variant. In addition, Visual Basic now supports unsigned integer data types (UShort, UInteger, and ULong), as well as the signed type SByte. For details, see Data Types in Visual Basic.
Interfaces describe the properties and methods of classes, but unlike classes, interfaces do not provide implementations. Use the Interface statement to declare interfaces; use the Implements statement to write code that puts the items described in the interface into practice. For details, see Interfaces in Visual Basic.
Delegates are objects that can call the methods of objects on your behalf and are sometimes described as type-safe, object-oriented function pointers. You can use delegates to let procedures specify an event handler method that runs when an event occurs. You can also use delegates with multithreaded applications. For details, see Delegates and the AddressOf Operator.
Shared members are properties, procedures, and fields that are shared by all instances of a class. Shared data members are useful when multiple objects need to use information that is common to all objects. You can use shared class methods without first creating an object from a class. For details, see Shared Members in Visual Basic.
You can use References to use objects defined in other assemblies. In Visual Basic 2008, references point to assemblies instead of type libraries. For details, see References and the Imports Statement.
Namespaces prevent naming conflicts by organizing classes, interfaces, and methods into hierarchies. For details, see Namespaces in Visual Basic.
Assemblies replace and extend the capabilities of type libraries by describing all the required files for a particular component or application. An assembly can contain one or more namespaces. For details, see Assemblies.
You can use attributes to provide additional information about program elements. For example, you can use an attribute to specify which methods in a class should be exposed when the class is used as a XML Web service. For details, see Attributes in Visual Basic.
You can use Visual Basic 2008 to write applications that can perform multiple tasks independently. A task that can hold up other tasks can execute on a separate thread, a process known as multithreading. By causing complicated tasks to run on threads that are separate from your user interface, multithreading makes your applications more responsive to user input. For details, see Multithreaded Applications.
Bit Shift Operators
Visual Basic 2008 now supports arithmetic left- and right-shift operations on integral data types (Byte, Short, Integer, and Long) as well as on unsigned types (UShort, UInteger, and ULong). Arithmetic shifts are not circular, which means the bits shifted off one end of the result are not reintroduced at the other end. The corresponding assignment operators are provided as well. For details, see Bit Shift Operators and Assignment Operators.
Loop Variable Declaration
You can use Visual Basic 2008 to declare a loop variable as part of a For or For Each loop. You can include an As clause for the variable in the For or For Each statement, provided no variable of that name has been declared outside the loop. The scope of a loop variable declared in this manner is the loop itself. For details, see For...Next Statement (Visual Basic) and For Each...Next Statement (Visual Basic).
What's New in the Visual Basic Language for Visual Basic 2005
In this version of Visual Studio, new language features in Visual Basic 2008 include loop continuation, guaranteed resource disposal, mixed access properties, unsigned data types, operator overloading, generic types, and much more. For more information, see What's New in the Visual Basic Language.