ADO Event Instantiation: Visual Basic

In order to handle ADO events in Visual Basic, you must declare a module-level variable using the WithEvents keyword. The variable can be declared only as part of a class module and must be declared at the module level. This is not as restrictive as it seems, however, because Visual Basic Form objects are also classes. The simplest way to handle ADO events is to declare a variable using WithEvents. The following example handles the ConnectComplete event for a Connection object:

' BeginEventExampleVB02  
Dim WithEvents connEvent As Connection  
Attribute connEvent.VB_VarHelpID = -1  
  
Private Sub Form_Load()  
Dim strConn As String  
  
   ' Create a new object with event  
   ' handling enabled.  
   strConn = "Provider=sqloledb;" & _  
      "Data Source=MyServer;" & _  
      "Initial Catalog=Northwind;" & _  
      "Integrated Security=SSPI;"  
   Set connEvent = New ADODB.Connection  
   connEvent.Open strConn  
End Sub  
  
Private Sub connEvent_ConnectComplete(ByVal pError As ADODB.Error, _  
    adStatus As ADODB.EventStatusEnum, _  
    ByVal pConnection As ADODB.Connection)  
Dim strMsg As String  
  
   If adStatus = adStatusErrorsOccurred Then  
      Select Case pError.Number  
         Case adErrOperationCancelled  
            ' The operation was cancelled in the  
            ' Will event. Notify the user and exit.  
            strMsg = "I'm sorry you can't connect right now." & vbCrLf  
            strMsg = strMsg & "Click OK to exit."  
            Unload Me  
         Case Else  
            strMsg = "Error " & Format(pError.Number) & vbCrLf  
            strMsg = strMsg & pError.Description  
            strMsg = strMsg & "Click OK to exit."  
            Unload Me  
      End Select  
   End If  
   frmWait.btnOK.Enabled = True  
End Sub  
' EndEventExampleVB02  

The Connection object is declared at the Form level using the WithEvents keyword to enable event handling. The Form_Load event handler actually creates the object by assigning a new Connection object to connEvent and then opens the connection. Of course, a real application would do more processing in the Form_Load event handler than is shown here.