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VB.Net - Program Structure

VB.Net Hello World Example

A VB.Net program basically consists of the following parts:

  • Namespace declaration

  • A class or module

  • One or more procedures

  • Variables

  • The Main procedure

  • Statements & Expressions

  • 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")
   End Sub
End Module

When the above code is compiled and executed, it produces 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 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

  • 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 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.

Compile & Execute VB.Net Program:

If you are using Visual Studio.Net IDE, take the following steps:

  • Start Visual Studio.

  • On the menu bar, choose File, New, Project.

  • Choose Visual Basic from templates

  • Choose Console Application.

  • 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.

  • 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.

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.

  • Save the file as helloworld.vb

  • 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.

  • 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.

  • You will be able to see "Hello World" printed on the screen.