| What does all this mean for Visual Basic? Plenty. VB.NET has been implemented as a fully compliant .NET language, which means that it compiles to managed code that runs on the CLR. It can use all the features of the .NET Framework and is fully on par with the new language C#, which was designed explicitly for .NET. VB.NET now supports inheritance, the explicit definition of interfaces, structured exception handling, strong type checking, free threading, and a more general event model. Visual Basic now does not take a back seat to any language. The basic syntax of VB.NET is the same as in previous versions, but there are some differences in details. On the whole, when you get used to it, the new features are more consistent to work with than the classical language. For example, there is now only one form of assignment, without a special Set statement for assigning object references. What everyone knows is that VB.NET is not compatible with older versions of Visual Basic, and converting a large program is not a trivial task. Microsoft supplies tools to help, but it is not an automated procedure. Thus VB6 will be around for a long time for legacy applications. Interoperating with legacy VB6 code is not the only interoperability scenario. Applications exist in many languages and many platforms. .NET has very strong support for interoperability. To go across platforms, you can make use of Web services and the SOAP protocol, a topic we discuss in Chapter 15. Within the Windows environment, you can make use of the Platform Invocation Services (PInvoke) and COM interoperability, a topic covered in Chapter 17. Because VB6 provides good support for COM, you can easily wrap VB6 code in COM objects and call them from VB.NET through the COM interop layer. You can also use ActiveX controls in VB.NET applications. The bottom line is that with VB.NET you do not have to leave anything behind, and you have an extremely powerful language and platform for writing new code going forward. There is a learning curve for this new language and environment, and that is what this book is all about.  |
