Siebel VB Language Reference > VB Language Reference >
IsNull Function
This standard VB function is used to determine whether a variant variable has the Null value. Syntax
IsNull(expression)
|
|
expression |
Any expression containing a variable of data type variant |
Returns
-1 (TRUE) if a variant expression contains the Null value, 0 (FALSE) otherwise. Usage
Null variants have no associated data and serve only to represent invalid or ambiguous results. Null is not the same as Empty, which indicates that a variant has not yet been initialized. Example
This example asks for ten test score values and calculates the average. If any score is negative, the value is set to Null. Then IsNull is used to reduce the total count of scores (originally 10) to just those with positive values before calculating the average. Sub Button_Click Dim arrayvar(10) Dim count as Integer Dim total as Integer Dim x as Integer Dim tscore as Single count = 10 total = 0 For x = 1 to count tscore = 88 If tscore<0 then arrayvar(x) = Null Else arrayvar(x) = tscore total = total + arrayvar(x) End If Next x Do While x <> 0 x = x - 1 If IsNull(arrayvar(x)) = -1 then count = count-1 End If Loop msgtext = "The average (excluding negative values) is: " msgtext = msgtext & Chr(10) & Format(total/count, "##.##") End Sub
Related Topics
IsDate Function IsEmpty Function IsNumeric Function VarType Function
|