Chapter 5: The Common Language Runtime

Overview

You’ve seen how to create simple applications and looked at how to create classes. Now it’s time not only to start tying these elements together, but also to learn how to dispose of some of the classes that you have created. The architects of .NET realized that all procedural languages require certain base functionality. For example, many languages ship with their own runtime that provides features such as memory management, but what if, instead of each language shipping with its own runtime implementation, all languages used a common runtime? This would provide languages with a standard environment and access to all of the same features. This is exactly what the common language runtime (CLR) provides.

The CLR manages the execution of code on the .NET platform. .NET provided Visual Basic developers better support for many advanced features, including operator overloading, implementation inheritance, threading, and the ability to marshal objects. Building such features into a language is not trivial. The CLR enabled Microsoft to concentrate on building this plumbing one time and then reuse it across multiple different programming languages. Because the CLR supports these features and because Visual Basic is built on top of the CLR, Visual Basic can use these features. The result is that, going forward, Visual Basic is the equal of every other .NET language, with the CLR eliminating many of the shortcomings of the previous versions of Visual Basic.

Visual Basic developers can view the CLR as a better Visual Basic runtime. However, this runtime, unlike the old standalone Visual Basic runtime, is common across all of .NET regardless of the underlying operating system. Thus, the functionality exposed by the CLR is available to all .NET languages; more important, all of the features available to other .NET languages via the CLR are available to Visual Basic developers. Additionally, as long as you develop using managed code - code that runs in the CLR - you’ll find that it doesn’t matter whether your application is installed on a Windows XP client or Vista client; your application will just run. The CLR provides an abstraction layer away from the details of the operating system.

This chapter gets down into the belly of the application runtime environment, not to examine how .NET abstracts you away from the operating system, but instead to look at some specific features related to how you build applications that run against the CLR. This includes an introduction to several basic elements of working with applications that run in the CLR, including the following:

• Elements of a .NET application

• Versioning and deployment

• Integration across .NET languages

• Microsoft Intermediate Language (MSIL)

• Memory management and the Garbage Collector (GC)