CodeNotes for VB.NET

Chapter 1
VB.NET AND THE .NET FRAMEWORK

Visual Basic is a creature that must evolve. Since its inception 10 years ago, each new version of the product has boasted additional capabilities to adapt to new technologies and paradigms. Visual Basic 5, for example, allowed developers to create ActiveX controls when Microsoft was attempting to foster the ActiveX proprietary technology. Visual Basic 6 introduced the Web Class Designer that greatly simplified the deployment of web applications using Dynamic HTML. VB.NET continues the evolutionary trend, but on a much grander scale. It is fair to say that VB.NET (what was once thought of as VB7) represents the most fundamental change in the Visual Basic language ever. Several aspects of the product that have remained consistent since VB's original release are different under VB.NET:


* The Visual Basic IDE is now integrated with VS.NET, Microsoft's next version of Visual Studio. This means that VB now shares its design environment with other Microsoft languages such as Visual C++.
* The Visual Basic Forms engine that drove form design in previous versions of VB has been replaced with Windows Forms, the new way to design desktop GUIs. Although Windows Forms still employs the same intuitive approach to application design (whereby one paints applications by dragging and dropping controls onto a form), it exposes many details abstracted in previous versions of VB.

* VB.NET has its own command-line compiler (called vbc.exe), allowing you to compile applications outside the Visual Basic environment. You can, for example, write VB source code using a text editor such as Notepad and then compile the source file from the command prompt.

In addition to these noteworthy changes, the language's syntax has been modified significantly. Array bounds, parameter passing, and control properties, for example, all behave differently under VB.NET. New features such as C++ try/catch error handling routines, multithreading, and object-oriented concepts such as inheritance have been added to the language. Microsoft has also removed numerous elements from the VB syntax. Among others, Variant, GoSub, IsNull, and IsMissing have all been retired.

Although each new version of a product raises compatibility issues, the magnitude of changes in VB.NET makes migration a prime concern for many developers. In Chapter 3, we investigate VB.NET's syntax changes in detail, as well as the Upgrade Wizard, which is designed to assist developers porting VB6 code to VB.NET.


The .NET Framework
To understand VB.NET, you must understand its new ecological niche -- the .NET Framework. Simply put, .NET is Microsoft's new strategy for the development and deployment of software. Depending on your interests and development background, you may already have a number of ideas about what exactly .NET is. As we will see in these CodeNotes,


* .NET fundamentally changes the way applications execute under the Windows operating system.
* With .NET, Microsoft is, in effect, abandoning its traditional stance, one that favors compiled components, and is embracing interpreted technology (similar in many ways to the Java paradigm).

* In addition to radically overhauling Visual Basic, .NET also brings about significant changes to Visual C++ and introduces a new language called C# (pronounced "C-sharp").