VB.net Variables – What is a Variable in Visual Basic

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.

In order for you to test your VB.net Code provided in this lesson, you can use our VB.net Online Compiler.

What is a Variable in Visual Basic?

Variable Declaration and Initializa...
Variable Declaration and Initialization in JAVA | Java Programming

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:

TypeExample
Integral typesSByte, Byte, Short, UShort, Integer, UInteger, Long, ULong and Char
Floating point typesSingle and Double
Decimal typesDecimal
Boolean typesTrue or False values, as assigned
Date typesDate
Basic Value Types

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

VB.net Variables Declaration

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

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 when the 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. 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

Test your Code Here!

Accepting Values from User

The Console class in the System namespace provides a function ReadLine for accepting input from the user and store 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!

Test your Code Here!

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

20 = g

Summary

In This Tutorial we’ve successfully discussed about the VB.net Variables and how to declare a variables in a program, also we discuss on how to store any data type Data in a variable name.


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