The const Keyword (Constant) in C#

The const Keyword (Constant) in C# Explained

In C# programming language, const is a keyword that is useful to declare constant fields in our applications. Generally, the constant field values are set at compile-time and those values will never change.

 

If we use const keyword to declare a constant field, then that field value cannot be changed throughout the application, so we should not use const keyword with the fields whose value will be changed at any time.

 

To define constant fields in C#, we need to use const keyword during the declaration of fields in our application and we can use constants with numbers, boolean values, strings or with null references.

 

It is mandatory to initialize constant fields with required values during the declaration, otherwise we will get compile-time errors in C# application.

 

In C#, the static modifier is not allowed to be used during the declaration of constant variables.

 

C# Constant Syntax

 

The following syntax shows how to define constant fields using const keyword in C#.

 const dataType fieldName = "value";

From the above syntax, we used a const keyword declare a constant variable by using the const keyword followed by the data type of the constant we intend to create and the field Name and lastly assigning a default value.

 

The following are the different ways of declaring and initializing a constant variables in C#.

 // Constant variables

const string name = "Musa Sule";

const string location = "Abuja, Nigeria";

const int age = 42;

const bool happy = true;

  

We created constant fields with some data types such as the string for name and location, integer (int) for age and bool for true or false.

 Constant (const) Example

The following code snippet is the example of defining and using constant fields in C# programming language with const keyword.

 

using System;

namespace CsharpnaijaTutorial

{

    class Program

    {

        static void Main(string[] args)

        {

            // Constant variables

            const string name = "Musa Sule";

            const string location = "Abuja, Nigeria";

            const int age = 42;

            const bool happy = true;

            // This will throw compile time error

            //name = "Sakinat Musa";

            Console.WriteLine($"Name: {name}");

            Console.WriteLine($"Location: {location}");

            Console.WriteLine($"Age: {age}");

            Console.Write($"Are you happy?: {happy}");

            Console.WriteLine("\nPress Enter Key to Exit..");

            Console.ReadLine();

        }

    }

}

 

From the above example, we created a constant fields with different data types and if we uncomment the commented code, then we will get a compile time error because we are trying to change the value of constant fields.

 

As earlier discussed, once the constant field is declare and initialized, then that field value must be same throughout the application.

 

When we run above C# program, we will get the output as shown below.

 

 Features of Constant in C#

The following are the important features of a constant variable in C#.

 

• Constant fields in C# can be created by using const keyword.
• The constant fields must be initialized during the time of declaration.
• Constant field values will be evaluated during compile time.
• Once values assigned to constant fields, then those values must be the same throughout the application.

Thank you

References

1.     Tutlane

2.     MicrosoftDocumentation