Visual Basic/Error Handling
Error handling in Visual Basic, an outline:
- On Error Goto <Label>
- On Error Goto 0
- On Error Resume Next
- If Err.Number = 0
- If Err.Number <> 0
- Resume
- Resume <Label>
- Resume Next
- Err.Description
- Err.Raise <Number>
Suppressing the error and detecting it using the non-zero error numberː
Set MyCollection = New Collection
MyCollection.Add "Item", "Item"
On Error Resume Next
MyCollection.Add "Item", "Item" 'This result in an error
MyErrNumber = Err.Number
On Error Goto 0 'Restore the absence of error handling
If MyErrNumber <> 0 Then
'Error occurred
MsgBox "Item already present in the collection."
End If
Creating an error handlerː
Sub Test()
On Error Goto ErrorHandler
...
Exit Sub
ErrorHandler:
...
End Sub
Creating an error handler that differentiates per error numberː
Sub Test()
On Error Goto ErrorHandler
...
Exit Sub
ErrorHandler:
Select Case Err.Number
Case 0
'No error
Case 5
'...
Case Else
'...
End Select
End Sub
See also Visual Basic/Effective Programming and Visual Basic/Coding Standards.