Enum basics C# with Example

From MSDN: 
An enumeration type (also named an enumeration or an enum) provides an efficient way to define a set 
of named integral constants that may be assigned to a variable. 
Essentially, an enum is a type that only allows a set of finite options, and each option corresponds to a number. By 
default, those numbers are increasing in the order the values are declared, starting from zero. For example, one 
could declare an enum for the days of the week: 
public enum Day 
{ 
Monday, 
Tuesday, 
Wednesday, 
Thursday, 
Friday, 
Saturday, 
Sunday 
} 
That enum could be used like this: 
// Define variables with values corresponding to specific days 
Day myFavoriteDay = Day.Friday; 
Day myLeastFavoriteDay = Day.Monday; 
// Get the int that corresponds to myFavoriteDay 
// Friday is number 4 
int myFavoriteDayIndex = (int)myFavoriteDay; 
// Get the day that represents number 5 
Day dayFive = (Day)5; 
By default the underlying type of each element in the enum is int, but byte, sbyte, short, ushort, uint, long and 
ulong can be used as well. If you use a type other than int, you must specify the type using a colon after the enum 
name: 
public enum Day : byte 
{ 
// same as before 
} 
 

The numbers after the name are now bytes instead of integers. You could get the underlying type of the enum as 
follows: 
Enum.GetUnderlyingType(typeof(Days))); 
Output: 
System.Byte 
Demo: .NET fiddle