Chapter 1. Introduction

Since its introduction in 1991, Microsoft Visual Basic has enjoyed unprecedented success. In fact, in slightly more than a decade , it has become the world's most widely used programming language, with an installed base of somewhere between three and five million developers (depending on the particular source you use and whether the estimate includes only the retail versions of the Visual Basic product or the hosted version of Visual Basic for Applications (VBA) as well).

The reason for this success is twofold. First, Visual Basic has excelled as a rapid application development (RAD) environment for corporate and commercial applications. Second, Visual Basic offers a programming language and development environment noted for its simplicity and ease of use, making it an extremely attractive choice for those new to programming.

With the release of its new .NET platform, Microsoft also released a new version of the Visual Basic language, Visual Basic .NET. VB.NET is a from-the-ground-up rewrite of Visual Basic that not only adds a number of new features, but also differs significantly from previous versions of Visual Basic. From a high-level view, two of these differences are especially noteworthy:

• Until the release of VB.NET, Microsoft focused on creating a unified version of VBA, the language engine used in Visual Basic, which could serve as a "universal batch language" for Windows and Windows applications. With Version 6 of Visual Basic, this goal was largely successful: VB 6.0 featured VBA 6.0, the same language engine that drives the individual applications in the Microsoft Office 2000 suite, Microsoft Project, Microsoft FrontPage, Microsoft Visio, and a host of popular third-party applications such as AutoDesk's AutoCAD and Corel's WordPerfect Office 2000. With the release of VB.NET, this emphasis on a unified programming language has, for the moment at least, faded into the background, as the hosted version of Visual Basic continues to be VBA rather than VB.NET.

• Since Version 4, Visual Basic had increasingly been used as a kind of "glue language" to access COM components and their object models, such as ActiveX Data Objects (ADO), Collaborative Data Objects (CDO), or the Outlook object model. Although VB.NET supports COM for reasons of backward compatibility, VB.NET is designed primarily to work with the .NET Framework rather than with COM.

You may be wondering why Microsoft would totally redesign a programming language and development environment that is so wildly successful. As we shall see, there is some method to this madness.