Explaining The Hello world example

In this video and article we explain the code we wrote in the hello world example

Review the actual code:

The code is organized by Namespace, Class and Method.
Code that is actually executed can only be defined inside Methods.

In the HelloWorld sample we created a new class and we defined a method inside this class
The Run method is part of the HelloWorld class
The Namespace of the HelloWorld class is Northwind.Training

Namespaces

Namespaces are used to organize the classes.
They used as the address of the class inside the solution.
The class HelloWorld is saved at Training folder under the Northwind solution.

Classes

With C#, code can be written only inside classes.
Class can contains Members such – Methods, properties, fields and more
The class HelloWorld contains a Method called Run() Inside the Method we called another method called Show()
and we sent the text to be displayed as parameter to the method.

Method

Method contains to code that is executed once the method is called.
The Run() method executes one line of code – it calls the Show() method

The method header definition:

Access modifier - Access modifier is a keyword used to specify the accessibility level of the method (or a class) It defined which code can see or use the method (or class)
There are Four access modifiers :

private – visible to members within this class and inner classes
protected – visible to members within this class and those which are inherits from this class
internal – visible to any code within my assembly (dll/exe)
public – visible to any code.
The Run() used in the HelloWorld has public access modifier.

Return value - Method can return a value to the caller The return value type should be define in the Method header before the Method name void is specify when a method doesn’t return a value
The Run() used in the HelloWorld has no return value so we specify void.

Method name - You can specify any name for the method as long as it is a valid C# name

() - in side the parentheses we specify the parameter the method receive
The Run() used in the HelloWorld receives no parameters so nothing is specify inside the parentheses

Calling a Method

To call a method we will specify the Method “Address” name space and the method name:

System.Windows.Forms.MessageBox.Show("Hello World");

System.Windows.Forms – is the namespace MessageBox – is the class name Show – is the method name which receives text as parameters

When we DbClick on the menu item Visual Studio generated a method which is called every time the menu item is being clicked inside this method we added the code to call the Run method of the HelloWorld class.

new Training.HelloWorld().Run();

new – a keyword to create a new instance of a class in this case we create a new instance of HelloWorld class which defined under the Training folder. and then we called the Run() method.