C# is provided as a part of Microsoft Visual Studio 7.0. In addition to C#, Visual Studio supports Visual Basic, Visual C++, and the scripting languages VBScript and JScript. All of these languages provide access to the Next Generation Windows Services (NWGS) platform, which includes a common execution engine and a rich class library. The .NET software development kit defines a "Common Language Subset" (CLS), a sort of lingua franca that ensures seamless interoperability between CLS-compliant languages and class libraries. For C# developers, this means that even though C# is a new language, it has complete access to the same rich class libraries that are used by seasoned tools such as Visual Basic and Visual C++. C# itself does not include a class library.
The rest of this chapter describes the essential features of the language. While later chapters describe rules and exceptions in a detail-oriented and sometimes mathematical manner, this chapter strives for clarity and brevity at the expense of completeness. The intent is to provide the reader with an introduction to the language that will facilitate the writing of early programs and the reading of later chapters.
The canonical “Hello, world” program can be written in C# as follows:
using System;
class Hello
{
static void Main() {
Console.WriteLine("Hello, world");
}
}
The default file extension for C# programs is .cs, as in hello.cs. Such a program can be compiled with the command line directive
csc hello.cs
which produces an executable program named hello.exe. The output of the program is:
Hello, world
Close examination of this program is illuminating:
