How to: Declare Enumerations - Visual Basic (original) (raw)

You create an enumeration with the Enum statement in the declarations section of a class or module. You cannot declare an enumeration within a method. To specify the appropriate level of access, use Private, Protected, Friend, or Public.

An Enum type has a name, an underlying type, and a set of fields, each representing a constant. The name must be a valid Visual Basic .NET qualifier. The underlying type must be one of the integer types—Byte, Short, Long or Integer. Integer is the default. Enumerations are always strongly typed and are not interchangeable with integer number types.

Enumerations cannot have floating-point values. If an enumeration is assigned a floating-point value with Option Strict On, a compiler error results. If Option Strict is Off, the value is automatically converted to the Enum type.

For information on names, and how to use the Imports statement to make name qualification unnecessary, see Enumerations and Name Qualification.

To declare an enumeration

  1. Write a declaration that includes a code access level, the Enum keyword, and a valid name, as in the following examples, each of which declares a different Enum.
Private Enum SampleEnum  
    SampleMember  
End Enum  
Public Enum SampleEnum2  
    SampleMember  
End Enum  
Protected Enum SampleEnum3  
    SampleMember  
End Enum  
Friend Enum SampleEnum4  
    SampleMember  
End Enum  
Protected Friend Enum SampleEnum5  
    SampleMember  
End Enum
  1. Define the constants in the enumeration. By default, the first constant in an enumeration is initialized to 0, and subsequent constants are initialized to a value of one more than the previous constant. For example, the following enumeration, Days, contains a constant named Sunday with the value 0, a constant named Monday with the value 1, a constant named Tuesday with the value of 2, and so on.
Public Enum Days  
    Sunday  
    Monday  
    Tuesday  
    Wednesday  
    Thursday  
    Friday  
    Saturday  
End Enum
  1. You can explicitly assign values to constants in an enumeration by using an assignment statement. You can assign any integer value, including negative numbers. For example, you may want constants with values less than zero to represent error conditions. In the following enumeration, the constant Invalid is explicitly assigned the value –1, and the constant Sunday is assigned the value 0. Because it is the first constant in the enumeration, Saturday is also initialized to the value 0. The value of Monday is 1 (one more than the value of Sunday); the value of Tuesday is 2, and so on.
Public Enum WorkDays  
    Saturday  
    Sunday = 0  
    Monday  
    Tuesday  
    Wednesday  
    Thursday  
    Friday  
    Invalid = -1  
End Enum

To declare an enumeration as an explicit type

Public Enum MyEnum As Byte  
    Zero  
    One  
    Two  
End Enum

See also