Error When Trying to Use .NET DLL in VB6

[DVader]

I've written a DLL in VB.NET and I am trying to use it in a VB6 application. When I run the application from either directly in VB6 or from the executable I get the following error message:

 

"Class does not support automation or does not support expected interface."

 

Here's a snapshot of the DLL code:

 

Option Explicit On 

Imports System
Imports Microsoft.Win32
Imports Microsoft.VisualBasic
Imports System.IO
Imports System.Security.Permissions

Imports System.Text

Imports CrystalDecisions.Enterprise
Imports CrystalDecisions.Enterprise.Viewing
Imports CrystalDecisions.Enterprise.Desktop.Report
Imports CrystalDecisions.ReportAppServer.Controllers
Imports CrystalDecisions.ReportAppServer.ClientDoc
Imports CrystalDecisions.ReportAppServer.DataDefModel

Imports CrystalDecisions.CrystalReports.TemplateEngine
Imports CrystalDecisions.ReportAppServer.ReportDefModel
Imports CrystalDecisions.ReportAppServer.CommonObjectModel
Imports CrystalDecisions.ReportAppServer.ObjectFactory

Imports System.Windows.Forms
Imports System.Runtime.InteropServices

Public Enum ReportServer As Integer
   Development = 0
   Test = 1
   Production = 2
End Enum

Public Enum DocumentType As Integer
   PDF = 0
   MSWord = 1
   MSExcel = 2
End Enum

<GuidAttribute("A366D469-A20A-4224-ACBA-6BDFE219E34A")> _
Public Interface _IBusinessObjectsServer

   Function RetrieveRepositoryReport(ByVal pReportName As String, _
                                     ByVal Server As ReportServer, _
                                     ByRef pParamList(,) As String, _
                                     ByVal DBUserName As String, _
                                     ByVal DBPassword As String, _
                                     Optional ByVal SQLServer As String = "", _
                                     Optional ByVal Database As String = "") As ReportClientDocument

   Sub ViewRepositoryReport(ByVal pReportName As String, _
                            ByVal Server As ReportServer, _
                            ByRef pParamList(,) As String, _
                            ByVal DBUserName As String, _
                            ByVal DBPassword As String, _
                            Optional ByVal SQLServer As String = "", _
                            Optional ByVal Database As String = "")

   Function ExportRepositoryReport(ByVal pReportName As String, _
                                   ByVal Server As ReportServer, _
                                   ByRef pParamList(,) As String, _
                                   ByVal DBUserName As String, _
                                   ByVal DBPassword As String, _
                                   ByVal pPathAndFilename As String, _
                                   ByVal pDocumentType As DocumentType, _
                                   Optional ByVal SQLServer As String = "", _
                                   Optional ByVal Database As String = "") As Boolean

End Interface

<System.Runtime.InteropServices.ProgId("BusinessObjectsReportServer"), _
ClassInterface(ClassInterfaceType.None), _
GuidAttribute("E1A6A3DF-6843-4899-BB35-5FB782F90056")> _
Public Class BOEReportServer

   Implements _IBusinessObjectsServer

   Friend bolShowExportButton As Boolean = False
   Friend bolShowGroupTreeButton As Boolean = False
   Friend bolDisplayGroupTree As Boolean = False
   Friend bolEnableDrillDown As Boolean = False
   Friend bolShowRefreshButton As Boolean = False
   Property ShowGroupTreeButton() As Boolean
       Get
           Return bolShowGroupTreeButton
       End Get
       Set(ByVal Value As Boolean)
           bolShowGroupTreeButton = Value
       End Set
   End Property
   Property ShowExportButton() As Boolean
       Get
           Return bolShowExportButton
       End Get
       Set(ByVal Value As Boolean)
           bolShowExportButton = Value
       End Set
   End Property
   Property DisplayGroupTree() As Boolean
       Get
           Return bolDisplayGroupTree
       End Get
       Set(ByVal Value As Boolean)
           bolDisplayGroupTree = Value
       End Set
   End Property
   Property EnableDrillDown() As Boolean
       Get
           Return bolEnableDrillDown
       End Get
       Set(ByVal Value As Boolean)
           bolEnableDrillDown = Value
       End Set
   End Property
   Property ShowRefreshButton() As Boolean
       Get
           Return bolShowRefreshButton
       End Get
       Set(ByVal Value As Boolean)
           bolShowRefreshButton = Value
       End Set
   End Property

   Public Function RetrieveRepositoryReport(ByVal pReportName As String, _
                                            ByVal Server As ReportServer, _
                                            ByRef pParamList(,) As String, _
                                            ByVal DBUserName As String, _
                                            ByVal DBPassword As String, _
                                            Optional ByVal SQLServer As String = "", _
                                            Optional ByVal Database As String = "") As ReportClientDocument Implements _IBusinessObjectsServer.RetrieveRepositoryReport

       CODE REMOVED...

   End Function
   Public Sub ViewRepositoryReport(ByVal pReportName As String, _
                                   ByVal Server As ReportServer, _
                                   ByRef pParamList(,) As String, _
                                   ByVal DBUserName As String, _
                                   ByVal DBPassword As String, _
                                   Optional ByVal SQLServer As String = "", _
                                   Optional ByVal Database As String = "") Implements _IBusinessObjectsServer.ViewRepositoryReport

       CODE REMOVED...

   End Sub
   Public Function ExportRepositoryReport(ByVal pReportName As String, _
                                          ByVal Server As ReportServer, _
                                          ByRef pParamList(,) As String, _
                                          ByVal DBUserName As String, _
                                          ByVal DBPassword As String, _
                                          ByVal pPathAndFilename As String, _
                                          ByVal pDocumentType As DocumentType, _
                                          Optional ByVal SQLServer As String = "", _
                                          Optional ByVal Database As String = "") As Boolean Implements _IBusinessObjectsServer.ExportRepositoryReport

       CODE REMOVED...

   End Function

End Class

 

I've checked the "Register for COM Interop" property of the DLL and added the AssemblyKeyFile line to the AssemblyInfo.vb

 

In the VB6 application I've added the DLL to the references. Here's a sample of the VB6 code:

 

Private Sub cmdReturnReport_Click()
 On Error GoTo Err_cmdReturnReport_Click

       Dim strParamList(5, 1) As String
       Dim strReportName As String
       
       strReportName = "EventsByPosition"
       strParamList(0, 0) = "Area"
       strParamList(0, 1) = "No"
       strParamList(1, 0) = "Region"
       strParamList(1, 1) = "No"
       strParamList(2, 0) = "From-Date"
       strParamList(2, 1) = "1995-01-01"
       strParamList(3, 0) = "To-Date"
       strParamList(3, 1) = "2004-12-31"
       strParamList(4, 0) = "Event-Type"
       strParamList(4, 1) = "J;V"
       strParamList(5, 0) = "@Position"
       strParamList(5, 1) = "EQUIPMENT MECHAN"
       '--------------------------------------------------------
       '-  Display the report . . .
       '--------------------------------------------------------
       Dim oRS As BusinessObjectsReportServer.BOEReportServer

       [b]Set oRS = New BusinessObjectsReportServer.BOEReportServer[/b]

       Call oRS.ViewRepositoryReport(strReportName, ReportServer_Development, strParamList, "HS50_Admin", "HS50_Admin")
       
Exit_cmdReturnReport_Click:
 Exit Sub
   
Err_cmdReturnReport_Click:
 MsgBox Err.Description & " - " & Err.Number

End Sub

 

The bold line above is the one giving the error. When I type in the lines that reference the DLL the intellisense works.

 

So what am I doing wrong?

[snarfblam]

I believe that you need to mark classes that will be used in VB6 with the ComClass attribute (and it might be a good idea to use some ComVisible attributes too). You also need to make your assembly visible to COM (apply the ComVisible attribute to the assembly in AssemblyInfo.vb or (in VB8) go to the project settings and under the "Application" tab click "Assembly Information" where you can check "Make assembly COM-visible").

[DVader]

One thing I should have mentioned in my first post was that this DLL needs to be used from either VB6 or .NET, so will any of those changes impact the DLL's use in a .NET application?

[snarfblam]

No. The attributes specify that extra accomodations be made available for COM interop (thunking and marshalling), but this does not affect the behavior within a completely managed environment.