UBound Function (Visual Basic)

發行項
11/18/2006

Returns the highest available subscript for the indicated dimension of an array.

Public Function UBound( _
   ByVal Array As System.Array, _ 
   Optional ByVal Rank As Integer = 1 _
) As Integer

Parameters

Array
Required. Array of any data type. The array in which you want to find the highest possible subscript of a dimension.

Rank
Optional. Integer. The dimension for which the highest possible subscript is to be returned. Use 1 for the first dimension, 2 for the second, and so on. If Rank is omitted, 1 is assumed.

Return Value

Integer. The highest value the subscript for the specified dimension can contain. If Array has only one element, UBound returns 0. If Array has no elements, for example if it is a zero-length string, UBound returns -1.

Exceptions

Exception type	Error number	Condition
ArgumentNullException	9	Array is Nothing
RankException	9	Rank is less than 1 or Rank is greater than the rank of Array.

See the "Error number" column if you are upgrading Visual Basic 6.0 applications that use unstructured error handling. (You can compare the error number against the Number Property (Err Object).) However, when possible, you should consider replacing such error control with Structured Exception Handling Overview for Visual Basic.

Remarks

Since array subscripts start at 0, the length of a dimension is greater by one than the highest available subscript for that dimension.

For an array with the following dimensions, UBound returns the values in the following table:

Dim a(100, 5, 4) As Byte

Call to UBound	Return value
`UBound(a, 1)`	100
`UBound(a, 2)`	5
`UBound(a, 3)`	4

You can use UBound to determine the total number of elements in an array, but you must adjust the value it returns to account for the fact that the subscripts start at 0. The following example calculates the total size of the array a in the preceding example:

Dim total As Integer
total = (UBound(A, 1) + 1) * (UBound(A, 2) + 1) * (UBound(A, 3) + 1)

The value calculated for total is 3030, which is 101 * 6 * 5.

Example

The following example uses the UBound function to determine the highest available subscript for the indicated dimension of an array.

Dim highest, bigArray(10, 15, 20), littleArray(6) As Integer
highest = UBound(bigArray, 1)
highest = UBound(bigArray, 3)
highest = UBound(littleArray)
' The three calls to UBound return 10, 20, and 6 respectively.

Requirements

Namespace: Microsoft.VisualBasic

Module: Information

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)

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