2.1 A First C# Program
Here is a simple C# program:
namespace FirstProgram {
using System;
class Example {
static void Main ( ) {
Console.WriteLine ("Hello world!");
}
}
}
A C# program is
composed of types
(typically classes) that we organize into namespaces. Each type
contains
function members (typically methods and properties), as well as
data
members (typically fields). Methods contain a series of statements
that are
executed
sequentially. In our program, we define a class named
Example that contains a method named
Main, which has a single statement that writes
Hello world! to the console
window. C# recognizes this method as the default entry point of
execution, so that's where the program begins.
The Console class
encapsulates
standard input/output functionality, providing methods such as
WriteLine. To use types from
another
namespace,
use the using directive. Since the
Console class resides in the
System namespace, we write
using System; similarly, types
from other namespaces could use our Example class
by using FirstProgram.
In C#, there are no standalone
functions; they are always associated
with a type, or, as we will see, instances of that type. Our program
is simple, and makes use of only static members, which means the
member is associated with its type, rather than instances of its
type. In addition, we make use of only void methods, which means
these methods do not return a value.
Throughout this book, most of the examples contain this stub code:
using System;
class Test {
static void Main ( ) {
...
}
}
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