VB.Net - Program Structure

Before we study basic building blocks of the VB.Net programming language, let us look a bare minimum VB.Net program structure so that we can take it as a reference in upcoming chapters.
A VB.Net program basically consists of the following parts −
Namespace declaration
Namespace declaration
A class or module
A class or module
One or more procedures
One or more procedures
Variables
Variables
The Main procedure
The Main procedure
Statements & Expressions
Statements & Expressions
Comments
Comments
Let us look at a simple code that would print the words "Hello World" −
Imports System
Module Module1
   'This program will display Hello World 
   Sub Main()
      Console.WriteLine("Hello World")
      Console.ReadKey()
   End Sub
End Module
When the above code is compiled and executed, it produces the following result −
Hello, World!

Let us look various parts of the above program −
The first line of the program Imports System is used to include the System namespace in the program.
The first line of the program Imports System is used to include the System namespace in the program.
The next line has a Module declaration, the module Module1. VB.Net is completely object oriented, so every program must contain a module of a class that contains the data and procedures that your program uses.
The next line has a Module declaration, the module Module1. VB.Net is completely object oriented, so every program must contain a module of a class that contains the data and procedures that your program uses.
Classes or Modules generally would contain more than one procedure. Procedures contain the executable code, or in other words, they define the behavior of the class. A procedure could be any of the following −

Function
Sub
Operator
Get
Set
AddHandler
RemoveHandler
RaiseEvent


Classes or Modules generally would contain more than one procedure. Procedures contain the executable code, or in other words, they define the behavior of the class. A procedure could be any of the following −
Function
Function
Sub
Sub
Operator
Operator
Get
Get
Set
Set
AddHandler
AddHandler
RemoveHandler
RemoveHandler
RaiseEvent
RaiseEvent
The next line( 'This program) will be ignored by the compiler and it has been put to add additional comments in the program.
The next line( 'This program) will be ignored by the compiler and it has been put to add additional comments in the program.
The next line defines the Main procedure, which is the entry point for all VB.Net programs. The Main procedure states what the module or class will do when executed.
The next line defines the Main procedure, which is the entry point for all VB.Net programs. The Main procedure states what the module or class will do when executed.
The Main procedure specifies its behavior with the statement
Console.WriteLine("Hello World") WriteLine is a method of the Console class defined in the System namespace. This statement causes the message "Hello, World!" to be displayed on the screen.
The Main procedure specifies its behavior with the statement
Console.WriteLine("Hello World") WriteLine is a method of the Console class defined in the System namespace. This statement causes the message "Hello, World!" to be displayed on the screen.
The last line Console.ReadKey() is for the VS.NET Users. This will prevent the screen from running and closing quickly when the program is launched from Visual Studio .NET.
The last line Console.ReadKey() is for the VS.NET Users. This will prevent the screen from running and closing quickly when the program is launched from Visual Studio .NET.
If you are using Visual Studio.Net IDE, take the following steps −
Start Visual Studio.
Start Visual Studio.
On the menu bar, choose File → New → Project.
On the menu bar, choose File → New → Project.
Choose Visual Basic from templates
Choose Visual Basic from templates
Choose Console Application.
Choose Console Application.
Specify a name and location for your project using the Browse button, and then choose the OK button.
Specify a name and location for your project using the Browse button, and then choose the OK button.
The new project appears in Solution Explorer.
The new project appears in Solution Explorer.
Write code in the Code Editor.
Write code in the Code Editor.
Click the Run button or the F5 key to run the project. A Command Prompt window appears that contains the line Hello World.
Click the Run button or the F5 key to run the project. A Command Prompt window appears that contains the line Hello World.
You can compile a VB.Net program by using the command line instead of the Visual Studio IDE −
Open a text editor and add the above mentioned code.
Open a text editor and add the above mentioned code.
Save the file as helloworld.vb
Save the file as helloworld.vb
Open the command prompt tool and go to the directory where you saved the file.
Open the command prompt tool and go to the directory where you saved the file.
Type vbc helloworld.vb and press enter to compile your code.
Type vbc helloworld.vb and press enter to compile your code.
If there are no errors in your code the command prompt will take you to the next line and would generate helloworld.exe executable file.
If there are no errors in your code the command prompt will take you to the next line and would generate helloworld.exe executable file.
Next, type helloworld to execute your program.
Next, type helloworld to execute your program.
You will be able to see "Hello World" printed on the screen.
You will be able to see "Hello World" printed on the screen.

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