Enumeration in c#

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;