A constant is an identifier used to represent a constant and predefined value that does not change during the program’s execution.
Constants are used to avoid repetition of literal values in the code and improve its clarity and readability.
In addition, the use of constants facilitates code updating and maintenance, as if you need to change the value of a constant, you only need to do it in one place.
Syntax of constants
The basic syntax for defining a constant in C# is as follows:
public const type name = value;- type: Specifies the data type of the constant
- name: Is the unique name given to the constant
- value: Is the constant value assigned to the constant
For example, let’s see how we can define a constant with the value of PI.
public const double PI = 3.14159;
Console.WriteLine(PI); // Output: 3.14159
PI = 3.5; // ❌ this would give an error, you cannot reassign a constant
Use of constants
Accessing constants
Constants are accessed using the class name followed by the constant name.
Console.WriteLine(Constants.Pi);Usage in expressions
Constants can be used in expressions instead of literal values to improve code readability and clarity.
double area = Constants.Pi * radius * radius;Naming convention
It is not mandatory, but it is relatively common to use constant names in uppercase to distinguish them from other variables.
public const double PI = 3.14159;Practical examples
Defining mathematical constants
public class MathematicalConstants
{
public const double Pi = 3.14159;
public const double Euler = 2.71828;
}Defining configuration constants
public class Configuration
{
public const int LoginAttemptsLimit = 3;
public const string DateFormat = "dd/MM/yyyy";
}