When you view a compiled WebClass (Internet Information Server application) in a Web browser, you may receive the following error message:

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This problem is caused by an error in the WebClass code that is not handled by any error handlers in the WebClass.

When you run the WebClass in debug mode in the Visual Basic Integrated Development Environment (IDE), the IDE traps the error and displays it in a message box. After you dismiss the message box, the debugger stops at the line of code that generates the error.

However, when you compile and browse the WebClass outside of the Visual Basic IDE, the WebClassRuntime traps the error and logs it in the Application log in the Event Viewer, along with a second event that indicates the "Application-defined or object-defined" error.

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To resolve this problem, you can read the application log and extract the error message. To do this on Microsoft Windows NT 4.0, perform the following steps:

1.	From the Start menu, point to Programs, point to Administrative Tools, and then click Event Viewer.
2.	In the Event Viewer window, on the Log menu, click Application.
3.	To view the logs, double-click the entries in the list.

The first log is an error that is generated by the WebClassRuntime and contains the following text: The second log is a warning from the VBRuntime and contains the actual error message: NOTE: Microsoft Windows 2000 does not report the actual error in the event log. To find the actual error message, you must create your own error handling in your WebClass procedures. This is also recommended for WebClasses on Windows NT so that you can produce custom error messages for your customers instead of the generic "Application-defined or object-defined error." In addition, to make sure that you catch all errors, you should implement an error handler in all of your WebClass methods.

To implement error handling in WebClasses, use the following sample code:

  Private Sub WebClass_Start()
  On Error GoTo ErrorHandler
    ...
    Your code goes here
    ...
  ErrorHandler:
    app.logEvent "error in method WebClass_Start: " & Err.Number & " " & Err.Description

    Select case Err.Number 
      Case 11
        Response.Write "<B>Your custom error message ...</B>"
      Case Else
        Response.Write "<B>Your generic error message ...</B>"
  End Sub
				

The App.LogEvent method creates an event log in the application log of the Web server. The source is the name of your WebClass.

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Private Sub WebClass_Start()
Dim i As Integer
    
    i = 1 / 0

End Sub
					

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

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