Enumerations
Enumerated type (also called enumeration or enum)
is a data type consisting of a set of named values.
A variable that has been declared as having an enumerated type can
be assigned any of the enumerators as a value. Enumerations make
the code more readable.
using System;
class CSharpApp
{
enum Days
{
Monday,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday,
Sunday
}
static void Main()
{
Days day = Days.Monday;
if (day == Days.Monday)
{
Console.WriteLine("It is Monday");
}
Console.WriteLine(day);
foreach(int i in Enum.GetValues(typeof(Days)))
Console.WriteLine(i);
}
}
In our code example, we create an enumeration for week days.
enum Days
{
Monday,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday,
Sunday
}
The enumeration is created with a
enum keyword.
The Monday, Tuesday ... barewords store in fact numbers 0..6.
Days day = Days.Monday;
We have a variable called day, which is of enumerated type Days.
It is initialized to Monday.
if (day == Days.Monday)
{
Console.WriteLine("It is Monday");
}
This code is more readable than if comparing
a day variable to some number.
Console.WriteLine(day);
This line prints Monday to the console.
foreach(int i in Enum.GetValues(typeof(Days)))
Console.WriteLine(i);
This loop prints 0..6 to the console. We get underlying
types of the enum values. For a computer, an enum is
just a number. The
typeof is an operator
used to obtain the System.Type object for a type. It is needed
by the
GetValues() method. This method returns an
array of the values of in a specified enumeration. And the
foreach keyword goes through the array, element
by element and prints them to the terminal.
We further work with enumerations.
using System;
class CSharpApp
{
public enum Seasons : byte
{
Spring = 1,
Summer = 2,
Autumn = 3,
Winter = 4
}
static void Main()
{
Seasons s1 = Seasons.Spring;
Seasons s2 = Seasons.Autumn;
Console.WriteLine(s1);
Console.WriteLine(s2);
}
}
Seasons can be easily used as enums. We can specify
the underlying type for the enum plus we can give exact
values for them.
public enum Seasons : byte
{
Spring = 1,
Summer = 2,
Autumn = 3,
Winter = 4
}
With a colon and a data type we specify the
underlying type for the enum. We also give each member a
specific number.
Console.WriteLine(s1);
Console.WriteLine(s2);
These two lines print the enum values to the console.
$ ./seasons.exe
Spring
Autumn
Output.
