PRB: How to Use Automation Error Code & Help from Visual Basic

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Sample Code Snippets

/* Compile options needed:
   standard MFC OLE project generated by AppWizard*/ 
				

1. The method in the Automation server that throws the dispatch exception should retain the help context and wCode as member variable of the automation object as in this function:

      void CMyObject::Exception()
      {
         m_nIDContext = <some context>;
         m_nSomeCode = <some code>;
         AfxThrowOleDispatchException(m_nSomeCode,"String",m_nIDContext);
      }
   						

2. The Automation server should expose a method that uses those member variables to start WinHelp or another help engine with the actual context from the exception as in this code:

      short CMyObject::GetError()
      {
         // From here you can use the member variable code
         // and context to start WinHelp or do whatever
         // help code you need to do ...
         AfxGetApp()->WinHelp(m_nIDContext);
         return m_nSomeCode;
      }
   						

3. The Visual Basic error handling routine should call the exposed error method in the Automation server when a dispatch exception occurs. Here is example Visual Basic code:

      Sub Command1_Click ()
         On Error GoTo EHandle
         Dim a As object
         Set a = CreateObject("TestAuto")
         ' Next line causes exception:
         a.exception
      EHandle:
         Msg = "The error message for error number "
         Msg = Msg & Err & " is:" & NL & NL
         Msg = Msg & """" & Error(Err) & """"
         MsgBox Msg  ' Display message.
         ' Next line starts WinHelp engine by calling method in server.
         a.GetError
         Exit Sub
      End Sub

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