IsError Function |
No
IsError(expression)
expression
Use: Required
Data Type: Variant
Variable to be evaluated to determine if its subtype is vbError.
Boolean (True or False).
Determines whether expression is a valid error value.
Use IsError only with variants. (Strongly typed variables can also be passed to IsError, but that's pointless; only variants have a vbError subtype and therefore have a chance of returning True.)
If the variant passed to IsError represents a valid error number, True is returned; otherwise, IsError returns False.
In this example, the SquarePositive function squares the values of only positive integers; if an integer isn't positive, the function returns a variant of subtype vbError:
Private Function SquarePositive(lngVal As Long) As Variant If lngVal > 0 Then SquarePositive = lngVal ^ 2 Else SquarePositive = CVErr(0) End If End Function Private Sub cmdSquare_Click() Dim varRetVal As Variant If IsNumeric(txtNumber.Text) Then varRetVal = SquarePositive(CLng(txtNumber.Text)) If IsError(varRetVal) Then MsgBox "Error: Enter a positive number!" Else txtNumber.Text = varRetVal End If Else txtNumber.Text = "" End If End Sub
You can create an error value by converting a real number using the CVErr function.
IsError evaluates the value returned by a function to determine whether the function executed without error, as the previous example shows.