Enumerators in C#

const int EngineCapacity = 1000;

If there was more than one engine capacity, then a range of constants could be defined, such as:

const int EngineCapacitySmall = 600;
const int EngineCapacityMedium = 1000;
const int EngineCapacityLarge = 1200;
const int EngineCapacityExtraLarge = 1800;

If even more constants were needed then this list could get pretty large, so it would be more convenient to group them into a single enumerator, by using syntax such as that shown below:

/// <summary>
/// Engine capacity enumerator
/// </summary>
enum EngineCapacity : int
{
  Small = 600,
  Medium = 1000,
  Large = 1200,
  ExtraLarge = 1800
}

Each enumerator is assigned a name (in this case it is EngineCapacity) and an optional data type. Here, the EngineCapacity enumerator is assigned a type of int, although being the default data type for enumerators it does not need to be specified - the following code will also work:

enum EngineCapacity : int
{
  Small = 600,
  Medium = 1000,
  Large = 1200,
  ExtraLarge = 1800
}

A value for the enumerator's type does not need to be specified - if it is not then the value of a type is incremented by one from the previous type (taking 0 as the first value). So in the example below, the small engine capacity will be 0 and the large engine capacity value will be 1001:

enum EngineCapacity : int
{
  Small,
  Medium = 1000,
  Large,
  ExtraLarge = 1800
}

Using the enumerator

Once the enumerator has been assigned it may be used in instances such as that shown below:

int RequiredCapacity = 1000;

if (RequiredCapacity == (int) EngineCapacity.ExtraLarge)
{
  //Check customer has the required maintenance contract
  //for the largest engine type
  if (CheckCustomerHasMaintenenceContract() == false)
    {
        return;
    }
}

Note that Visual Studio understands enumerators, and will usefully include their value types in the intellisense for that enumerator.