A constant is a data item whose value cannot be changed during the program's execution. In Visual Basic .NET, you can declare a constant using the Const keyword. The syntax for declaring a constant is as follows:
Const constantName As dataType = value
Here, constantName is the name of the constant, dataType is the data type of the constant, and value is the initial value assigned to the constant.
Here are some examples of using constants in Visual Basic .NET:
Example 1:
Const PI As Double = 3.14159
Dim radius As Double = 5
Dim area As Double = PI * radius * radius
Console.WriteLine("Area of circle = " & area)
In this example, we declare a constant named PI of type Double and assign it the value 3.14159. We use this constant to calculate the area of a circle using the formula A = πr².
Example 2:
Const MAX_VALUE As Integer = 100
Dim value As Integer = 75
If value > MAX_VALUE Then
Console.WriteLine("Value is greater than " & MAX_VALUE)
Else
Console.WriteLine("Value is less than or equal to " & MAX_VALUE)
End If
In this example, we declare a constant named MAX_VALUE of type Integer and assign it the value 100. We use this constant in an If statement to compare the value of a variable named value. If value is greater than MAX_VALUE, we print a message indicating that the value is greater than the maximum value. Otherwise, we print a message indicating that the value is less than or equal to the maximum value.
Example 3:
Const GREETING As String = "Hello, world!"
Console.WriteLine(GREETING)
In this example, we declare a constant named GREETING of type String and assign it the value "Hello, world!". We print the value of this constant using the Console.WriteLine statement.
These are just a few examples of how you can use constants in Visual Basic .NET. Constants are often used to define values that are used repeatedly in a program, making the code easier to understand and maintain.