Learn the fundamental concepts of programming in C# such as data structures, loops, and methods.

Become a C# Programmer

This highly interactive module begins with a simple “Hello, World!” program and proceeds to cover common concepts such as conditional statements, loops, and methods in C#. It also reflects on the idea of arrays as well as the power they give to the programmer to write better code. Finally, it dives deeper in order to teach us about delegates in C# through interactive challenges and exercises.

C# for Programmers: A Practical Guide

There are basic elements that all C# executable programs have, and that’s what we’ll concentrate on for this first lesson, starting off with a simple C# program.

>**Warning:** C# is **case-sensitive**

Below is a very simple **C#** application.

It is a console application that
prints out the *message* `"Hello, World!"` 

// Namespace Declaration
using System;

// Program start class
class HelloWorld
{
    // Main begins program execution.
    static void Main()
    {
        // Write to console
      Console.WriteLine("Hello, World!"); 
    }
}

The program has **four** *primary* elements: 
* a *namespace* declaration 
* a *class* 
* the `Main` method 
* a program *statement*

>**Note:** Since **C#** is *case-sensitive* the word `Main` is not the same as its *lowercase* spelling, `main`. 

## The "using" Directive

**Line 2** of the above program is using a 

* **Directive**
  * It declares that the *current* file can use members of the indicated *namespace* without using the member's fully qualified name. 

Without this directive, all references to the identifier `Console` would have to be preceded by `System` and a period, because `Console` is a member of the `System` *namespace*. 

## Class Definition

The class *declaration*, class `HelloWorld`, contains 

* Data  
* *Method* definitions that your program uses to execute
* Single static method named `Main`

* The **method** is the entry point of the application
* The `Main` method may be declared with a parameter to accept an *array* of *strings* and may return an *integer* value. 
* The *array* of *strings* passed to the method represent the *command line* arguments used when executing the program
  * This program doesn't use *command line* arguments, and so the method wasn't declared to accept **any** arguments

## Body of the Main Method

* The `Main` method specifies its behavior with the `Console.WriteLine(…)` statement
* The `Console` is a *class* in the `System` 

* `namespace.WriteLine(…)` is a method in the `Console` class
* We use the “.”, dot, operator to separate subordinate program elements. 
> Note that we could also write this statement as `System.Console.WriteLine(…)`. 
* This follows the pattern **namespace.class.method** as a fully qualified statement. Had we left out the using `System` declaration at the top of the program, it would have been mandatory for us to use the fully qualified form `System.Console.WriteLine(…)`. This statement is what causes the string, **“Hello, World!”** to print on the console screen.

This lesson acquaints you with the Hello World program and gives a basic introduction to C#

Hello World!

A simple Hello World Program