Enums in

About Enums

You can use Enumeration types whenever you have a fixed set of constant values. Using an enum gives one a type-safe way of interacting with constant values. Defining an enum is done through the enum keyword. An enum member is referred to by prepending it with the enum name and a dot (e.g. Status.Active).

Each enum member is an association of a name and an int value. If the first member does not have an explicit value, its value is set to 0. If no value is explicitly defined for an enum member, its value is automatically assigned to the previous member's value plus 1.

enum Season
{
    Spring,     // Auto set 0
    Summer = 2, // Set the value 2
    Autumn,     // Auto set 3
    Winter = 7  // Set the value 7
}

Enums are very declarative. Compare the following two method calls:

Users.WithStatus(1)
Users.WithStatus(Status.Active)

For someone reading the code, the second version (with enum) will be easier to comprehend.

Numeric type Enums

While the default numeric type of the values is int, it can be changed by explicitly specifying any other integral numeric type.

The following enum use the byte numeric type for its values:

enum Priority : byte
{
    Low = 0,
    Medium = 127,
    High = 255
}

Convert to an Enum member

You should always consider using an enum whenever you want to model something like a Boolean. Besides the aforementioned readability benefits, enums have another advantage over Booleans: new values can always be added to an enum, whereas a Boolean value will only ever be true or false. Using an enum is thus more future proof.

enum Status
{
    Inactive = 0,
    Active = 1
}

Status active = (Status) 1;
active == Status.Active; // True

Note that while one can cast integer values to an enum, doing so can lead to unexpected results when the integer value doesn't map to some enum value:

Status status = (Status) 2;
status == Status.Inactive; // False
status == Status.Active;   // False

Parsing an enum

It's sometimes useful to convert a string to an enum member based on its name with Enum.Parse:

var input = "Inactive";
Status status = (Status)Enum.Parse(typeof(Status), input);
// Inactive

To check if a name or a value exists in the enum, you can use Enum.TryParse or Enum.IsDefined, both return a Boolean indicating if the enum member exists:

bool doesExist = Enum.IsDefined(typeof(Status), "Inexistent");
// False

More examples and best practices are available here.