Yet relatively few VB programmers take advantage of interface-based programming. And interface-based programming itself does not allow a derived class to inherit the functionality of a base class; only virtual base classes can be inherited using the Implements keyword. While the object-oriented character of previous versions of VB may be in doubt, there is no question that VB. NET is an object-oriented programming language.
In fact, even if VB. Traditionally, one of the problems of calling routines written in other languages from Visual Basic or of calling Visual Basic routines from other languages is that such inter-language calls presuppose a common type system. For instance, until the addition of the AddressOf operator, which allows us to pass a pointer to a function or subroutine, there was no way to provide a callback function, which is required by most Win32 API enumeration functions.
As another example, it is expected that members of structures passed to Win32 API functions be aligned on their natural boundaries, something that VB programmers had great difficulty accomplishing. Problems of type compatibility tended to occur most often when scripted applications were used to call and pass arguments to COM components. NET platform removes these difficulties by providing a common type system.
Ultimately, all data types are either classes or structures defined by or inherited from the. This common type system means that. NET components will be truly language-independent and that a. NET component written in one language will be seamlessly interoperable with. NET components written in any other. NET language. The problem of incompatible types simply disappears. On the surface, VB has retained its old type system. VB still supports the Long data type, for instance, although it is now a bit data type instead of the bit data type of VB 4 through VB 6.
String literals can contain newline sequences. You can put comments after implicit line continuations, inside initializer expressions, and among LINQ expression terms. Given code such as Threading. Sleep , Visual Basic used to look up the namespace "Threading", discover it was ambiguous between System.
Threading and System. Threading, and then report an error. Visual Basic now considers both possible namespaces together. If you show the completion list, the Visual Studio editor lists members from both types in the completion list. You can implement readonly interface properties using a readwrite property. The interface guarantees minimum functionality, and it does not stop an implementing class from allowing the property to be set.
When writing doc comments, you get smart editor and build support for validating parameter names, proper handling of crefs generics, operators, etc. Partial module and interface definitions. Region directives inside method bodies. You can put Region… End Region delimiters anywhere in a file, inside functions, and even spanning across function bodies. Overrides definitions are implicitly overloads. If you add the Overrides modifier to a definition, the compiler implicitly adds Overloads so that you can type less code in common cases.
The compiler used to give an error that CObj … was not a constant when used in attribute constructions. Previously the following code yielded errors that prevented you from declaring IMock or from calling GetDetails if these had been declared in C :. Now the compiler will use normal overload resolution rules to choose the most appropriate GetDetails to call, and you can declare interface relationships in Visual Basic like those shown in the sample.
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Current version Visual Basic Previous versions Visual Basic NET Visual Basic Comments allowed in more places within statements In Visual Basic Public Sub Main cmd. Fix Double Conversion. Fix Object Conversion. Fix Single Conversion. Int Double Conversion. Int Object Conversion. Int Single Math. Ceiling Double Math. Floor Double Math. Round Double Math. Truncate Double This optimization allows code to run faster -- up to twice as fast for code that does a large number of conversions to integer types.
Round s ' Result: Note that this truncates rather than rounds floating-point values. Visual Basic 15 Tuples Tuples are a lightweight data structure that most commonly is used to return multiple values from a single method call. Ordinarily, to return multiple values from a method, you have to do one of the following: Define a custom type a Class or a Structure.
This means that VB. NET can be used to create a wide range of applications and components, including the following:. Accessing application object models such as those of the individual applications in the Microsoft Office suite using COM automation. Most importantly, for the first time with the release of VB.
NET, Visual Basic becomes an all-purpose development environment for building Internet applications, an area in which it has traditionally been weak.
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