PRB: Implementing Stock Error Event in Custom OLE Control

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic for Windows 16-bit and 32-bit, version 4.0

SYMPTOMS

Visual Basic generates an error message if the MFC Class Wizard's stock Error event is implemented in a custom OLE Control.

For example, if you go to the OLE Events tab in the MFC Class Wizard and add the stock Error event, you will get the following definition in the control's ODL file:

   dispinterface _DTestEvents
    {
     properties:
     //  Event interface has no properties

     methods:
      // NOTE - ClassWizard will maintain event information here.
      //    Use extreme caution when editing this section.
      //{{AFX_ODL_EVENT(CTestCtrl)

      [id(DISPID_ERROREVENT)] void Error(short Number, BSTR*
       Description, SCODE Scode, BSTR Source, BSTR HelpFile,
       long HelpContext, boolean* CancelDisplay);

       .
       .

      //}}AFX_ODL_EVENT
      };

   Private Sub Test1_Error(Number As Integer, Description As String, _
            Scode As Error, Source As String, HelpFile As String, _
            HelpContext As Long, CancelDisplay As Boolean)

   End Sub

RESOLUTION

To avoid the error generated by Visual Basic, you need to change the event definition of the stock error event in the ODL such that the third parameter is of type long instead of SCODE:

[id(DISPID_ERROREVENT)] void Error(short Number, BSTR* Description, long Scode, BSTR Source, BSTR HelpFile, long HelpContext,boolean*CancelDisplay);

This will change the third parameter in the Visual Basic event stub from "Scode As Error" to "Scode As Long," and the error will no longer be generated.

STATUS

This behavior is by design.