This document discusses enumerations in C#. It explains that an enumeration allows assigning names to integer values, with values defaulting to 0, 1, 2, etc. It provides an example enumeration for shapes and uses it in a program to calculate areas. The document also covers initializing enum values to specific integers, the default integer base type, and type conversions between enums and their base type.

1. Enumeration in C#
Dr. Neeraj Kumar Pandey

2. Enumeration
 An enumeration is a user defined integer type which provides a way for
attaching names to numbers.
 The enum keyword automatically enumerates a list of words by assigning
them values 0,1,2….
enum shape
{
Circle,
Square,
Triangle
}
 This can be written as:- enum shape{ Circle,Square,Triangle}
 Here ,Circle has the value 0,Square has the value 1 and Triangle has the
value 2.

3. Enumeration Program
class EnumTest
{
public static void Main()
{
Area area= new Area();
area.AreaShape(15,Area.Shape.Circle);
area.AreaShape(15,Area.Shape.Square);
area.AreaShape(15,(Area.Shape)1);
area.AreaShape(15,(Area.Shape) 10);
}
}
using System;
class Area
{
public enum Shape
{
Circle,
Square
}
public void AreaShape(int x, Shape shape)
{
double area;
switch(shape)
{
case Shape.Circle:
area= Math.PI*x*x;
Console.WriteLine("Circle Area="+area);
break;
case Shape.Square:
area=x*x;
Console.WriteLine("Square Area="+area);
break;
default:
Console.WriteLine("Invalid Input");
break;
}
}
}

4. Enumeration Initialization
 Default value of the first enum member is 0 and that of each subsequent
is incremented by one.
 We can assign specific values for different members.
enum color
{
Red=4,
Green=Red+3,
Black=Red+Green+2,
Yellow=5
}
enum color
{
Red=4,
Green=9,
Black=3,
Yellow=5
}

5. Enumeration Initialization
 If the declaration of an enum member has no initializer, then its value is set implicitly as
follows:-
• If it is the first member, its value is zero.
• Otherwise, its value is obtained by adding one to the value of the previous member.
Consider the following enum declaration:-
enum Alphabet
{
A,
B=5,
C,
D=20,
E
}
Following enum declaration is not
valid because the declarations are
circular
enum ABC
{
A,
B=C,
C
}

6. Enumerator Base Type
 By default, the enum type is int. However, we can declare explicitly a base
type for each enum.
 The valid base type for enum are:- byte,sbyte,short,ushort,int,uint,long
and ulong.
enum Position : byte
{
Off,
On
}
enum shape: long
{
Circle,
Square=100,
Rectangle
}

7. Enumerator Type Conversion
 Enum types can be converted to their base type and back again with an
explicit conversion using a cast.
Enum values
{
value0,
value1,
value2,
value3
}
values u1=(values) 1;
int a= (int)u1;