Enumeration (enum) in C#

Enumeration (enum) in C# is a special value type that defines a set of named constants. It improves code readability by giving meaningful names to numeric values.

Example: Enum of Days in a week

enum Days { Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday }

• Value type: Stored as integers by default (can use other integral types like byte, short, long).
• Default underlying type: int (starting from 0 unless specified).
• Custom values: You can assign explicit numeric values to members.
• Strongly typed constants: Prevents use of invalid values.
• Improves readability: Use enum Days.Monday instead of 0.
• Useful in switch statements for handling predefined options.
• Scoped to their type: Prevents accidental mixing of unrelated constants.

Declaring and Using an enum

Enumeration is declared using the enum keyword directly inside a namespace, class or structure.

Example: Using Enumeration within the same class to store the book with their index.

Book: Java at Index:4
Book: Python at Index:3
Book: Kotlin at Index:2
Book: Javascript at Index:1
Book: cSharp at Index:0

Explanation: In the above example we create a enum (Enumeration) to declare the name of books and access their index value which is starting from the 0 in the enum and type cast the value to get the values in numeric from.

Custom Value Assignment in enum

By default, the first member starts at 0, but you can assign custom values.

Example: Another example of an enum is to show the month name with its default value.

The value of jan in month enum is 0
The value of feb in month enum is 1
The value of mar in month enum is 2
The value of apr in month enum is 3
The value of may in month enum is 4

Explanation: In the above code we create a enum with month name, its data members are the name of months like jan, feb, mar, apr, may. Then print the default integer values of these enums. An explicit cast is required to convert from enum type to an integral type.

Using enum in Conditional Statements

Example: Using enum to find the shapes to find their perimeter.

Explanation: In the example, an enum Shapes is defined with Circle = 0 and Square = 1. The class Perimeter has a method peri() that takes one parameter for side/radius and another (0 or 1) to identify the shape using Shapes.Circle or Shapes.Square. If the value is 0, it’s a circle; otherwise, it’s a square.

Custom Value Initialization in enum

The default value of first enum member is set to 0 and it increases by 1 for the further data members of enum. However, the user can also change these default value.

enum days {

day1 = 1,
day2 = day1 + 1,
day3 = day1 + 2
.
.

}

Changing the Data Type of enum

By default, enum values are of type int, but you can change them to byte, short, long, etc.

Example: Custom value initialization in enum.

Note: Now, if the data member of the enum member has not been initialized, then its value is set according to the rules stated below: 

• If it is the first member, then its value is set to 0 otherwise.
• It sets out the value which is obtained by adding 1 to the previous value of the f enum data member.

Example: Changing the type of enum’s data member

The electric switch is ON

Explanation: By default the base data type of enumerator in C# is int. However, the user can change it as per convenience like byte, byte, short, short, int, uint, long, etc In this example, we change the data type as byte.