VB.net Variables – Declaration and Initialization of Variables in VB

VB.net Variables

A VB.net variables is nothing more than a name for a storage space that our programs can access.

In VB.net, each variable has a type that governs the memory size and layout, the range of values that may be stored within that memory, and the set of operations that can be applied to the variable.

A variable is used in VB.NET to store a value that can be used later in the program. We’ll learn how to declare and initialize variables in this section.

What is a Variable in Visual Basic?

A variable is a short name for the value of a specific data type that is stored in computer memory.

Each variable in VB.net has a specific data type that determines its size, range, and fixed memory location.

In any programming language, we can use variables to execute multiple operations and alter data values.

The basic value types provided in VB.net can be categorized as:

VB.net also allows defining other value types of variables like Enum and reference types of variables like Class.

VB.net Variables Declaration

The declaration of a variable is simple and requires a variable name and data type followed by a Dim. A Dim is used in Class, Module, structure, Sub, and procedure.

The syntax for variable declaration in VB.Net is:

'Syntax for variable declaration in VB.Net'

[ < attributelist > ] [ accessmodifier ] [[ Shared ] [ Shadows ] | [ Static ]]
[ ReadOnly ] Dim [ WithEvents ] variablelist

1. attributelist

attributelist is a list of attributes that apply to the variable. Optional.

2. accessmodifier

accessmodifier defines the access levels of the variables, it has values as – Public, Protected, Friend, Protected Friend and Private. Optional.

3. Shared

Shared declares a shared variable, which is not associated with any specific instance of a class or structure, rather available to all the instances of the class or structure. Optional.

4. Shadows

Shadows indicate that the variable re-declares and hides an identically named element, or set of overloaded elements, in a base class. Optional.

5. Static

Static indicates that the variable will retain its value, even after termination of the procedure in which it is declared. Optional.

6. ReadOnly

ReadOnly means the variable can be read, but not written. Optional.

7. WithEvents

WithEvents specifies that the variable is used to respond to events raised by the instance assigned to the variable. Optional.

8. Variablelist

Variablelist provides the list of variables declared.

Each variable in the variable list has the following syntax and parts:

'syntax for each variable in the variable list'

variablename[ ( [ boundslist ] ) ] [ As [ New ] datatype ] [ = initializer ]

variablename

variablename − is the name of the variable.

boundslist

boundslist − optional. It provides list of bounds of each dimension of an array variable.

New

New − optional. It creates a new instance of the class when the Dim statement runs.

datatype

datatype − Required if Option Strict is On. It specifies the data type of the variable.

initializer

initializer − Optional if New is not specified. An expression that is evaluated and assigned to the variable when it is created.

Some valid variable declarations along with their definition are shown here:

'variable declarations along with their definition'

Dim StudentID As Integer
Dim StudentName As String
Dim Salary As Double
Dim count1, count2 As Integer
Dim status As Boolean
Dim exitButton As New System.Windows.Forms.Button
Dim lastTime, nextTime As Date

Variable Initialization in VB.net

Variables in VB.net are initialized (assigned a value) with an equal sign followed by a constant expression.

The general form of initialization is:

//general form of initialization

variable_name = value;

For example:

'variable initialization'

Dim pi As Double
pi = 3.14159

You can initialize a variable at the time of declaration as follows:

'initializing the variable at the time'

Dim StudentID As Integer = 100
Dim StudentName As String = "Angel Jude Suarez"

Example Code for the various VB.net Variable Types

Try the following example which makes use of various vb.net types of variable

'following example of various types of variables'

Module variablesNdataypes
   Sub Main()
      Dim a As Short
      Dim b As Integer
      Dim c As Double
      
      a = 10
      b = 20
      c = a + b
      Console.WriteLine("a = {0}, b = {1}, c = {2}", a, b, c)
      Console.ReadLine()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result:

a = 10, b = 20, c = 30

You can test the above example here! ➡ VB.net Online Compiler

Accepting Values from User

The Console class in the System namespace provides a function ReadLine for accepting input from the user and storing it into a variable.

For example:

'accepting user input'

Dim message As String
message = Console.ReadLine

The following example demonstrates it:

Module variablesNdataypes
   Sub Main()
      Dim message As String
      Console.Write("Enter message: ")
      message = Console.ReadLine
      Console.WriteLine()
      Console.WriteLine("Your Message: {0}", message)
      Console.ReadLine()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result (assume the user inputs Hello IT SOURCECODERS!)

Enter message: Hello IT SOURCECODERS!
Your Message: Hello IT SOURCECODERS!

You can test the above example here! ➡ VB.net Online Compiler

Lvalues and Rvalues

There are two kinds of expressions:

1. lvalue

lvalue − An expression that is an lvalue may appear as either the left-hand or right-hand side of an assignment.

2. rvalue

rvalue − An expression that is an rvalue may appear on the right- but not the left-hand side of an assignment.

Variables are lvalues and so may appear on the left-hand side of an assignment. Numeric literals are rvalues and so may not be assigned and can not appear on the left-hand side.

Following is a valid statement:

Dim g As Integer = 20

But the following is not a valid statement and would generate a compile-time error

20 = g

Summary

In this tutorial we’ve successfully discussed the VB.net Variables and how to declare a variable in a program, also we discussed how to store any data type Data in a variable name.

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