C# Language Specification

C# is a simple, modern, object oriented, and type-safe programming language derived from C and C++. It will
immediately be familiar to C and C++ programmers. C# aims to combine the high productivity of Visual Basic
and the raw power of C++.
C# is provided as 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
Microsoft .NET platform, which includes a common execution engine and a rich class library. The Microsoft
.NET platform defines a “Common Language Specification” (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.

Getting started
The canonical “hello, world” program can be written as follows:
using System;
class Hello
{
static void Main() {
Console.WriteLine("hello, world");
}
}
-The source code for a C# program is typically stored in one or more text files with a file extension of .cs, as in
hello.cs. Using the command-line compiler provided with Visual Studio, 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:
· The using System; directive references a namespace called System that is provided by the Microsoft
.NET Framework class library. This namespace contains the Console class referred to in the Main method.
Namespaces provide a hierarchical means of organizing the elements of a class library or program. A
“using” directive enables unqualified use of the types that are members of the namespace. The “hello,
world” program uses Console.WriteLine as a shorthand for System.Console.WriteLine.
· The Main method is a member of the class Hello. It has the static modifier, and so it is a method on the
class Hello rather than on instances of this class.
· The main entry point for a program—the method that is called to begin execution—is always a static
method named Main.

-The “hello, world” output is produced through the use of a class library. The language does not itself
provide a class library. Instead, it uses a common class library that is also used by languages such as Visual
Basic and Visual C++.
For C and C++ developers, it is interesting to note a few things that do not appear in the “hello, world” program.
· The program does not use a global method for Main. Methods and variables are not supported at the global
level; such elements are always contained within type declarations (e.g., class and struct declarations).
· The program does not use either “::” or “->” operators. The “::” is not an operator at all, and the “->”
operator is used in only a small fraction of programs. The separator “.” is used in compound names such as
Console.WriteLine.
· The program does not contain forward declarations. Forward declarations are never needed, as declaration
order is not significant.
· The program does not use #include to import program text. Dependencies among programs are handled
symbolically rather than textually. This approach eliminates barriers between programs written in different
languages. For example, the Console class could be written in another language.

.

.

Click Here to Download