What is C# enum and how to use it?
Defining C# enum
C# enum (enumerator) is a user defined integer type which provides a way for attaching names to numbers, thus increasing the flexibility of code. The enum keyword automatically enumerates a list of worlds by assigning those values 0, 1, 2 and so on. This C# enum facility provides an alternative means of creating ‘constant variable names. The syntax of a C# enum statement is given below:
enum area
{
Length,
Breadth
}
This C# enum initialization can also be written as follows:
enum area {Length, Breadth}
Here Length has the value 0, Breadth has the value 1.
Other examples of C# enum are:
enum days { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday}
enum position { off, on}
C# enum initialization
Earlier mentioned that by default C# enum member is set 0 and each of the subsequent member is incremented by one. C# enum members are initialized as follows
enum Color
{
Red = 1,
Blue = 3,
Green = 7,
Yellow = 5
}
It is also possible to have expressions as long as they use the already defined enum members.
Example
enum color
{
Red = 1,
Blue = Red+2,
Green = Red+Blue+3,
Yellow = Blue+5
}
If the declaration of an enumerator member has no initialize, 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 C# enum declaration
enum Alphabet
{
A,
B=5,
C,
D=20,
E
}
The member A is set to zero, Since the member B is explicitly given the value 5, the value of C is set to 6 (i.e., 5+1). Similarly, E is set to 21.
C# enum base types
By default the type of an enumerator is int. However, we can declare explicitly a base type for each C# enum. The valid base types are:
Byte, sbyte, short, ushort, int, uint, long, ulong
Example
enum position
{
Off,
On
}
enum shape : long
{
Circle.
Square =100,
Triangle
}
C# enum type conversion
C# enum types can be converted to their base type and back again with an explicit conversion using a cast.
Example
Enum Values
{
Value0,
Value1,
Value2
Value3
}
…………
…………
Values u1 = (Values) 1;
int a = (int) u1;
…………..
…………..
The exception to this that the literal 0 can be converted to an enum type without a cast.
i.e., Values u0 = 0;
Sample program to illustrate the use of C# enum type
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;
}}
class enumtest
{
public static void main()
{
Area area = new Area();
area.AreaShape(15,AreaShape.Circle);
area.AreaShape(15,AreaShape.Square);
area.AreaShape(15,(Area.Shape)1);
area.AreaShape(15,AreaShape)10);
}}
Output
Circle Area=706.8583
Square Area=225.00000
Square Area=225.00000
Invalid Input
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