Enumeration (enum) is a value data type in C#. It is mainly used to assign the names or string values to integral constants, that make a program easy to read and maintain. For example, the 4 suits in a deck of playing cards may be 4 enumerators named Club, Diamond, Heart, and Spade, belonging to an enumerated type named Suit.
- Enumeration is declared using the enum keyword directly inside a namespace, class, or structure.
- The Objective of the enum is to define our data types(Enumerated Data Types).
- Enum can be used to define the custom integrals to the strings.
- By default the base type of enum is int.
Declaring and Using an enum
An enum is declared using the enum keyword followed by the enumeration name and its members.
Example 1: Using Enumeration within the same class to store the book with their index.
C# // Using enum in C# using System; class Program { // Enum declaration enum Books { cSharp, Javascript, Kotlin, Python, Java } public static void Main(string[] args) { // Get the value of the enum Console.WriteLine("Book: Java at Index:"+ (int)Books.Java); Console.WriteLine("Book: Python at Index:"+ (int)Books.Python); Console.WriteLine("Book: Kotlin at Index:"+ (int) Books.Kotlin); Console.WriteLine("Book: Javascript at Index:"+ (int)Books.Javascript); Console.WriteLine("Book: cSharp at Index:"+ (int)Books.cSharp); } } OutputBook: 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.
Syntax
enum Enum_variable
{
string_1…;
string_2…;
.
.
}
In above syntax, Enum_variable is the name of the enumerator, and string_1 is attached with value 0, string_2 is attached value 1 and so on. Because by default, the first member of an enum has the value 0, and the value of each successive enum member is increased by 1. We can change this default value.
Custom Value Assignment in enum
By default, the first member starts at 0, but you can assign custom values.
Example 2: Another example of an enum is to show the month name with its default value.
C# // C# program to illustrate the enums // with their default values using System; class Geeks { // making an enumerator 'month' enum month { // following are the data members jan, feb, mar, apr, may } static void Main(string[] args) { // getting the integer values of data members.. Console.WriteLine("The value of jan in month " + "enum is " + (int)month.jan); Console.WriteLine("The value of feb in month " + "enum is " + (int)month.feb); Console.WriteLine("The value of mar in month " + "enum is " + (int)month.mar); Console.WriteLine("The value of apr in month " + "enum is " + (int)month.apr); Console.WriteLine("The value of may in month " + "enum is " + (int)month.may); } } OutputThe 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 3: Using enum to find the shapes to find their perimeter.
C# // C# program to illustrate the Enums using System; class Perimeter { // declaring enum public enum Shapes { Circle, Square } public void Peri(int val, Shapes shape) { if (shape == Shapes.Circle) { // Output the circumference Console.WriteLine("Circumference of the circle is " + 2 * 3.14 * val); } else { // Output the perimeter of the square Console.WriteLine("Perimeter of the square is " + 4 * val); } } } class Geeks { // Main Method static void Main(string[] args) { Perimeter o = new Perimeter(); // Display the perimeter of the circle o.Peri(3, Perimeter.Shapes.Circle); // Display the perimeter of the square o.Peri(4, Perimeter.Shapes.Square); } } Explanation: In the above example we create an enum and define the two strings which are Circle and Square by default initialized to value 0 and similarly, Square is assigned value 1 inside the class Perimeter. There is also one member function peri() which takes one parameter as a value to initializes the side/radius. Another parameter is used to judge the shape whether it is a circle or square in the form of an integer value(0 or 1). We directly use the Shapes. A circle which returns 0 and identifies the shape is equal to a circle else it is 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 4: Custom value initialization in enum.
C# // C# program custom enum values using System; class Geeks { // Enum declaration enum days { Sun, Mon, tue, Wed }; enum random { A, B=6, C, D}; static void Main(string[] args) { // days enum values are started 0 by default Console.WriteLine("Sun = " + (int)days.Sun); Console.WriteLine("Mon = " + (int)days.Mon); // The value started from 0 by default Console.WriteLine("A = " + (int)random.A); // Explicitly assigning values: B is assigned 6, // so C automatically gets the next value, which is 7 Console.WriteLine("B = " + (int)random.B); // The value become 7 as C is next to B Console.WriteLine("C = " + (int)random.C); } } Explanation: In the above example as shown by default enum values are initialised with the 0 as in days we saw that the values are Sun(0) and Mon(1). But when we assign the B=6 in a random enum it’s next C initializes the value as 7. If we change the value of the first data member of the enum, further data members of the enums will increase by 1.
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 5: Changing the type of enum’s data member
C# // C# program to illustrate the changing // of data type of enum members using System; // changing the type to byte using : enum Button : byte { // OFF denotes the Button is // switched Off... with value 0 OFF, // ON denotes the Button is // switched on.. with value 1 ON } class Geeks { static void Main(string[] args) { // Declaring a variable of type byte // and assigning it the value of ON byte b = 1; if (b == (byte)Button.OFF) { Console.WriteLine("The electric switch is Off"); } else if (b == (byte)Button.ON) { Console.WriteLine("The electric switch is ON"); } else { Console.WriteLine("byte cannot hold such" + " large value"); } } } OutputThe 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.
When to Use enum?
- When you have a set of related integral constants.
- When you want type safety (unlike const values, which can be assigned to any int).