Error When Trying to Use .NET DLL in VB6

[DVader]

Ive 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."

Heres 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

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

In the VB6 application Ive added the DLL to the references. Heres 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 DLLs 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.