In general, an enumeration is a type whose members consist of a defined set of named constant values with a common underlying data type. For example, you might have an enumeration type Color defined with an underlying integer data type, and this enumeration has a member, Blue, with the underlying integer value of 5. However, where .NET structures its enumerations to interoperate interchangeably as both values and as value type objects, ABL structures and manages .NET enumerations, like all class instances that it references, only as objects.