Constants, Literals and Enumerations in C#

In this tutorial we are going to understand the importance of constants, literals and enums.  Const and enums are C# constructs which are used to make code more readable and easy to maintain.

Constant

Constant are just like C# variable with the exception that you have to assign a value at declaration and you can’t change its value once declared.

How to use Constant
You can make any variable constant by putting “const” keyword at the start of that variable.

Example

const float PI = 3.14;

Note that it is a common practice that when you declare a constant variable you spell it in upper case. It is not compulsory but it is a good programming practice. When others will see your code it would be easy for them to understand that it is a constant.

Why use Constant

1. If you have a variable whose value won’t change in throughout your program then you may want it to be constant because you don’t want its value to be changed accidently.
2. It is a good programming practice that you don’t use hard coded value in your program because it might get difficult for other programmers when they see your code or even for you if you see your code after some time that why you have used those hard coded value.
3. By using constant it is easy to maintain your code because if in future you want to change that value you can change that at declaration and all your code will remain same where as if you use hard coded value it will become difficult to upgrade your change.

Example : bad practice

class Program
   {
     static void Main(string[] args)
     {
        Console.Write("Enter radius = ");
        int radius = Convert.ToInt16(Console.ReadLine());
        float area = 3.14f * radius * radius;  //bad practice what is 3.14
        Console.WriteLine("The area of circle with {0} radius is {1}.", radius, area);
        Console.ReadLine();
     }
   }

Example: good practice

class Program
   {
     static void Main(string[] args)
     {
        const float PI = 3.14f;
        Console.Write("Enter radius = ");
        int radius = Convert.ToInt16(Console.ReadLine());
        float area = PI * radius * radius;  //good practice PI is constant to use for cirlce
        Console.WriteLine("The area of circle with {0} radius is {1}.", radius, area);
        Console.ReadLine();
     }
   }

Enumeration (Enum)

If you have a program with a lot of constant that all related to each other then it is good if you can group them together at one place. For this purpose you can use enumeration.

How to use Enumeration
You can use enumeration by using enum word followed by the name you want to specify for your enum and then you can list the entire constant in enum separated by comma.

Example
Consider you have following constants.

const int GRADE_A = 80;
const int GRADE_B = 70;
const int GRADE_C = 60;
const int GRADE_D = 50;  

you can create enum for these constants like

enum Grades {
        GRADE_A = 80,
        GRADE_B = 70,
        GRADE_C = 60,
 	GRADE_D = 50  
}

Note that you can’t use space when you defining an element. If needed you can use underscore ( _ ).

Where to define a Enumeration

One thing you should know that you have to define you enum outside the main function. You can’t use them in a function.

Value of Enumeration

1. If no value is assigned to first constant then it will have default value that is 0.
2. If no value is assigned to constant other than first, it will have value one more than the previous value.

Example

enum Score {
	NILL,   //will have default value of 0
	ONE,   // it will have one more than previous one that is 1
	TEN = 10,   //will have assign value
	ELEVEN	 //will have one more than previous one that is 11
}

Type of Enumerations

By default the enumerations are int type that means you can only assign int values to its member. But you can define types that are numeric in nature that are byte, sbyte, short, ushort, int, uint, long or ulong.

How to define a type of Enumeration
You can define a type of enumeration by just putting colon (:) after the name and giving the type you want to assign.

Example

enum Grades : byte
{
     GRADE_A = 80,
     GRADE_B = 70,
     GRADE_C = 60,
     GRADE_D = 50  
}

Working Example of Enumeration

namespace Enums
{
    class Program
    {
        enum Temperature
        {
            FREEZING_POINT,
            BOILING_POINT = 100
        }
        static void Main(string[] args)
        {
            int freezing_Poing = (int)Temperature.FREEZING_POINT;  
                                    //has to explicitly type cast into integer
            int boiling_Point = (int)Temperature.BOILING_POINT;  
                                    //has to explicitly type cast into integer
            Console.WriteLine("The freezing point of water is {0} Celsius.", freezing_Poing);
            Console.WriteLine("The boiling point of water is {0} Celsius.", boiling_Point);
            Console.ReadLine();
        }
    }
}

Practice

Create a program with string constant.
Enums are very helpful when dealing with a lot of constant. Create example with ten enum elements.

Find if string enums are possible or create any alternative.

<< Data Types: Type conversion