C# 4.0 Pocket Reference, 3rd Edition

A First C# Program

Here is a program that multiplies 12 by 30, and prints the result, 360, to the screen. The double forward slashes indicate that the remainder of a line is a comment:

using System;                 // Importing namespace

class Test                    // Class declaration
{
  static void Main()          // Method declaration
  {
    int x = 12 * 30;          // Statement 1
    Console.WriteLine (x);    // Statement 2
  }                           // End of method
}                             // End of class

At the heart of this program lies two statements. Statements in C# execute sequentially. Each statement is terminated by a semicolon. The first statement computes the expression 12 * 30 and stores the result in a local variable, named x, which is an integer type. The second statement calls the Console class’s WriteLine method, to print the variable x to a text window on the screen.

A method performs an action in a series of statements, called a statement block—a pair of braces containing zero or more statements. We defined a single method named Main.

Writing higher-level functions that call upon lower-level functions simplifies a program. We can refactor our program with a reusable method that multiplies an integer by 12, as follows:

using System;

class Test
{
  static void Main()
  {
    Console.WriteLine (FeetToInches (30));    // 360
    Console.WriteLine (FeetToInches (100));   // 1200
  }

  static int FeetToInches (int feet)
  {
    int inches = feet * 12;
    return inches;
  }
}

A method can receive input data from the caller by specifying parameters and output data back to the caller by specifying a return type ...