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C# 5.0 Pocket Reference by Ben Albahari, Joseph Albahari

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A First C# Program

Here is a program that multiplies 12 by 30, and prints the result, 360, to the screen. The double forward slash indicates 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 lie two statements. Statements in C# execute sequentially and are 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. We defined a ...

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