How to: Declare A Constant
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How to: Declare A Constant

You use the Const statement to declare a constant and set its value. By declaring a constant, you assign a meaningful name to a value. Once a constant is declared, it cannot be modified or assigned a new value.

You declare a constant within a procedure or in the declarations section of a module, class, or structure. Class or structure-level constants are Private by default, but may also be declared as Public, Friend, Protected, or Protected Friend for the appropriate level of code access.

The constant must have a valid symbolic name (the rules are the same as those for creating variable names) and an expression composed of numeric or string constants and operators (but no function calls).

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To declare a constant

  • Write a declaration that includes an access specifier, the Const keyword, and an expression, as in the following examples:

    Public Const DaysInYear = 365
    Private Const WorkDays = 250
    

    When Option Strict is On, you must declare a constant explicitly by specifying a data type (Boolean, Byte, Char, DateTime, Decimal, Double, Integer, Long, Short, Single, or String). When Option Strict is Off, the constant is assigned a data type by the compiler. For more information, see Constant and Literal Data Types.

To declare a constant with Option Strict On

  • With Option Strict On, write a declaration that includes the As keyword and an explicit data type, as in the following examples:

    Public Const MyInteger As Integer = 42
    Private Const DaysInWeek As Short = 7
    Protected Friend Const Funday As String = "Sunday"
    

    You can declare multiple constants on a single line, although your code is more readable if you declare only a single constant per line. If you declare multiple constants on a single line, they must all have the same access level (Public, Private, Friend, Protected, or Protected Friend).

To declare multiple constants on a single line

  • Separate the declarations with a comma and a space, as in the following example:

    Public Const Four As Integer = 4, Five As Integer = 5, Six As Integer = 44
    
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