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Static (Visual Basic)

  • Článok

Specifies that one or more declared local variables are to continue to exist and retain their latest values after termination of the procedure in which they are declared.

Remarks

Normally, a local variable in a procedure ceases to exist as soon as the procedure stops. A static variable continues to exist and retains its most recent value. The next time your code calls the procedure, the variable is not reinitialized, and it still holds the latest value that you assigned to it. A static variable continues to exist for the lifetime of the class or module that it is defined in.

Rules

  • Declaration Context. You can use Static only on local variables. This means the declaration context for a Static variable must be a procedure or a block in a procedure, and it cannot be a source file, namespace, class, structure, or module.

    You cannot use Static inside a structure procedure.

  • The data types of Static local variables cannot be inferred. For more information, see Local Type Inference.

  • Combined Modifiers. You cannot specify Static together with ReadOnly, Shadows, or Shared in the same declaration.

Behavior

When you declare a static variable in a Shared procedure, only one copy of the static variable is available for the whole application. You call a Shared procedure by using the class name, not a variable that points to an instance of the class.

When you declare a static variable in a procedure that isn't Shared, only one copy of the variable is available for each instance of the class. You call a non-shared procedure by using a variable that points to a specific instance of the class.

Example

The following example demonstrates the use of Static.

Function updateSales(ByVal thisSale As Decimal) As Decimal
    Static totalSales As Decimal = 0
    totalSales += thisSale
    Return totalSales
End Function

The Static variable totalSales is initialized to 0 only one time. Each time that you enter updateSales, totalSales still has the most recent value that you calculated for it.

The Static modifier can be used in this context:

Dim Statement

See also