Error Handler

To do effective error handling, you must write them into each and every routine. What a pain! There are many ways to do error handling, from coding it yourself to purchasing add-on tools that will do most of the code writing for you.

This tip is for those who prefer to do it themselves. This is a good idea, because you have much more control over it. Also, another important part of error handling is writing the error to a file. This will save you tons of time in development and also help with technical support problems. Instead of trying to get information on the error message from the user, they can simply send the error log. This tip incorporates that philosophy.

Declare

Global Const errExit = 0
Global Const errResume = 1
Global Const errNext = 2
Global Const errSelect = 3

Code

Public Function ErrorHandler(iErrorNumber As Integer, sErrText As String, 
                               iErrOption As Integer) As Integer

Dim sMessage As String
Dim iReturn As Integer

     'Create message string

     sMessage = "Error #:" & Str(iErrorNumber) & " - "

     sMessage = sMessage & sErrText

     'Save to error log file

     ErrWriteLogFile sMessage

     Select Case iErrOption

           Case errExit

                 MsgBox sMessage, vbCritical, _

                       "Exiting program..."

                 GoTo errHandlerEnd

           Case errResume

                 MsgBox sMessage, vbCritical, "Error"

                 ErrorHandler = errResume

           Case errNext

                 MsgBox sMessage, vbCritical, "Error"

                 ErrorHandler = errNext

           Case errSelect

                 iReturn = MsgBox(sMessage, vbCritical + _

                       vbAbortRetryIgnore, "Error")

                 Select Case iReturn

                       Case Is = vbAbort

                             GoTo errHandlerEnd

                       Case Is = vbRetry

                             ErrorHandler = errResume

                       Case Is = vbIgnore

                             ErrorHandler = errNext

                 End Select

     End Select

     Exit Function

errHandlerEnd:

     MsgBox "Click OK to Exit Program"

     End

End Function

Public Sub ErrWriteLogFile(sLogMsg As String)

     Dim sFile As String

     Dim lFile As Long

     Dim sErrDir As String

     On Error GoTo errWriteLogFileErr

     sErrDir = App.Path

     lFile = FreeFile

     sFile = sErrDir & "\" & App.EXEName & ".err"

     Open sFile For Append As lFile

     Print #lFile, Format$(Now, "General Date") & ": " _

           & sLogMsg

     Close #lFile

     GoTo errWriteLogFileExit

errWriteLogFileErr:

     MsgBox Str(Err) + "-" + Error$, vbCritical, _

           "Unable to Write Error Log"

     Exit Sub

errWriteLogFileExit:

End Sub

Example

This is a sample of how you could use this tip:

Dim R As Long

Dim I As Integer

On Error GoTo ErrorHandler1

     For I = 3000 To 100000

           DoEvents

     Next I

ErrorHandler1:

     R = ErrorHandler(iErrorNumber:=Err.Number, sErrText:=Err.Description, iErrOption:=errNext)

Even though this tip was written in Visual Basic 4.0, it can be easily modified for any other version of Visual Basic. It’s also easy to modify for your particular needs.

 

This tips is reprinted from the VB Tips & Tricks Volume 1 book.
Some parts of this tips was submitted by: George Graff