Enumerators

Enum, also known as Enumerator, is a structure for grouping together some integral constants. The constants are basically of the type int.

Following is the syntax for creating an enum:

index


              1234567
            
enum EnumName 
{
    Const1,
    Const2,
    Const3,
    ...
}

By default the first element of an enum has the value 0, the second element has a value 1 and so on.

For-example:

index


              12345678910
            
enum Days
{
    Monday,		// 0
    Tuesday,	// 1
  	Wednesday,	// 2
    Thursday,	// 3
    Friday,		// 4
    Saturday,	// 5
    Sunday		// 6
}

We can access the values of these constants using the enumName.constantName syntax.

For-example:

index


              123456789101112131415161718192021222324
            
using System;

enum Days
{
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
}

class ConsoleApp
{
    static void Main(string[] args)
    {
        // Explicitly converting the enum elements to 'int' and then outputting them
        Console.WriteLine((int)Days.Monday);        // 0
        Console.WriteLine((int)Days.Wednesday);     // 2
        Console.WriteLine((int)Days.Friday);            // 4
        Console.WriteLine((int)Days.Sunday);            // 6
    }
}

Note that in the above example we explicitly need to convert the constant into an int datatype since these constants are of type Days by default, which means that the enum Days is a new datatype which we created. Therefore, it can be stored into a variable of type Days:

This is useful in places like switch statements.

For-example:

index


              123456789101112131415161718192021222324252627282930313233343536373839404142434445464748
            
using System;

enum Days
{
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
}

class ConsoleApp
{
    static void Main(string[] args)
    {
        Days day = Days.Friday;

        switch (day)
        {
            case Days.Monday:
                Console.WriteLine("It is Monday");
                break;
            case Days.Tuesday:
                Console.WriteLine("It is Tuesday");
                break;
            case Days.Wednesday:
                Console.WriteLine("It is Wednesday");
                break;
            case Days.Thursday:
                Console.WriteLine("It is Thursday");
                break;
            case Days.Friday:
                Console.WriteLine("It is Friday");
                break;
            case Days.Saturday:
                Console.WriteLine("It is Saturday");
                break;
            case Days.Sunday:
                Console.WriteLine("It is Sunday");
                break;
            default:
                Console.WriteLine("Invalid Day");
                break;
        }
    }
}

We can also manually assign values to the enum constants. The unassigned constants take up incremented values of the previous elements:

index


              123456789101112131415161718192021222324252627
            
using System;

enum Days
{
    Monday,
    Tuesday,
    Wednesday = 5,
    Thursday,
    Friday,
    Saturday = 10,
    Sunday
}

class ConsoleApp
{
    static void Main(string[] args)
    {
        // Explicitly converting the enum elements to 'int' and then outputting them
        Console.WriteLine((int)Days.Monday);
        Console.WriteLine((int)Days.Tuesday);
        Console.WriteLine((int)Days.Wednesday);
        Console.WriteLine((int)Days.Thursday);
        Console.WriteLine((int)Days.Friday);
        Console.WriteLine((int)Days.Saturday);
        Console.WriteLine((int)Days.Sunday);
    }
}

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Seção 2. Capítulo 10