Introduction

The Significance of .NET and C#

In order to understand the significance of .NET, it is useful to remind ourselves of the nature of many of the Windows technologies that have appeared in the past 10 years or so. Although they may look quite different on the surface, all of the Windows operating systems from Windows 3.1 (introduced in 1992) through Windows Server 2003 have the same familiar Windows API at their core. As we’ve progressed through new versions of Windows, huge numbers of new functions have been added to the API, but this has been a process of evolving and extending the API rather than replacing it.

The same can be said for many of the technologies and frameworks that we’ve used to develop software for Windows. For example, COM (Component Object Model) originated as OLE (Object Linking and Embedding). At the time, it was, to a large extent, simply a means by which different types of Office documents could be linked, so that, for example, you could place a small Excel spreadsheet in your Word document. From that it evolved into COM, DCOM (Distributed COM), and eventually COM+ - a sophisticated technology that formed the basis of the way almost all components communicated, as well as implementing transactions, messaging services, and object pooling.

Microsoft chose this evolutionary approach to software for the obvious reason that it is concerned about backward compatibility. Over the years, a huge base of third-party software has been written for Windows, and Windows wouldn’t have enjoyed the success it has had if every time Microsoft introduced a new technology it broke the existing code base!

While backward compatibility has been a crucial feature of Windows technologies and one of the strengths of the Windows platform, it does have a big disadvantage. Every time some technology evolves and adds new features, it ends up a bit more complicated than it was before.

It was clear that something had to change. Microsoft couldn’t go on forever extending the same development tools and languages, always making them more and more complex in order to satisfy the conflicting demands of keeping up with the newest hardware and maintaining backward compatibility with what was around when Windows first became popular in the early 1990s. There comes a point where you have to start with a clean slate if you want a simple yet sophisticated set of languages, environments, and developer tools, which makes it easy for developers to write state-of-the-art software.

This fresh start is what C# and .NET are all about. Roughly speaking, .NET is a framework - an API - for programming on the Windows platform. Along with the .NET Framework, C# is a language that has been designed from scratch to work with .NET, as well as to take advantage of all the progress in developer environments and in our understanding of object-oriented programming principles that have taken place over the past 20 years.

Before we continue, we should make it clear that backward compatibility has not been lost in the process. Existing programs will continue to work, and .NET was designed with the ability to work with existing software. Presently, communication between software components on Windows almost entirely takes place using COM. Taking account of this, .NET does have the ability to provide wrappers around existing COM components so that .NET components can talk to them.

It is true that you don’t need to learn C# in order to write code for .NET. Microsoft has extended C++, provided another new language called J#, and made substantial changes to Visual Basic to turn it into the more powerful language Visual Basic .NET, in order to allow code written in either of these languages to target the .NET environment. These other languages, however, are hampered by the legacy of having evolved over the years rather than having been written from the start with today’s technology in mind.

This site will equip you to program in C#, while at the same time provide the necessary background in how the .NET architecture works. We will not only cover the fundamentals of the C# language but also go on to give examples of applications that use a variety of related technologies, including database access, dynamic Web pages, advanced graphics, and directory access. The only requirement is that you be familiar with at least one other high-level language used on Windows - either C++, Visual Basic, or J++.