VB.NET Language in a Nutshell, Second Edition

Name

LBound Function

Class

Microsoft.VisualBasic.Information

Syntax

LBound(array[, rank])

array (required; any array)

An array whose lower bound is to be determined

rank (optional; Integer)

The dimension whose lower bound is desired

Return Value

An Integer whose value is 0

Description

Determines the lower boundary of a specified dimension of an array. The lower boundary is the smallest subscript you can access within the specified array.

Rules at a Glance

• Unless it is passed an invalid argument, the LBound function always returns 0.

• If array is uninitialized, it generates an ArgumentNullException error when passed to the LBound function. You can prevent this by comparing array to Nothing, as in the following code fragment:

  If Not oArray Is Nothing Then

• To determine the lower limit of the first dimension of an array, set rank to 1, set it to 2 for the second, and so on.

• If rank isn’t specified, 1 is assumed.

Programming Tips and Gotchas

Since VB.NET does not allow you to change the lower bound of an array, the LBound function would appear to be superfluous except for reasons of backward compatibility. Its continued use may be a good idea, though, in the event that a future version of VB.NET allows you to set the lower boundary of an array.

VB.NET/VB 6 Differences

Since VB 6 offers a number of ways to set the lower bound of all arrays or a specific array, the LBound function is particularly useful when iterating the elements of an array. In VB.NET, its use is a matter of choice.

See Also

UBound ...