Problem running VB DLL in Internet Explorer

**exr** · September 2nd, 2007, 10:55 AM

The project I am doing requires custom functionality from a DLL executed from with Internet Explorer.

The DLL is written in VB 2005. The DLL resides on the local machine, where it is registered with Regasm. The DLL implements iObjectSafety in order to allow IE to load it with an OBJECT tag.

IE loads the DLL without error. The first time you call a function from the DLL it works like a charm. The second time you call any DLL function, it fails with "Object doesn't support this property or method".

Here is sample code for the DLL:

Code:

Imports System.Runtime.InteropServices
<ComImport()> _
<Guid("CB5BDC81-93C1-11CF-8F20-00805F2CD064")> _
<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Public Interface IObjectSafety
    Function GetInterfaceSafetyOptions(ByRef iid As Guid, ByRef pdwSupportedOptions As Integer, ByRef pdwEnabledOptions As Integer) As Integer
    Function SetInterfaceSafetyOptions(ByRef iid As Guid, ByVal dwOptionSetMask As Integer, ByVal dwEnabledOptions As Integer) As Integer
End Interface

<Microsoft.VisualBasic.ComClass(iSiteTest.ClassId, iSiteTest.InterfaceId, iSiteTest.EventsId)> _
<System.Serializable()> _
Public Class myTest
    Implements IObjectSafety
    Public Const ClassId As String = "6DB79AF2-F661-44AC-8458-62B06BFDD9E4"
    Public Const InterfaceId As String = "E7E27E4B-9AE3-47f9-8B0D-7A2EB8DEB17C"
    Public Const EventsId As String = "E754DF7F-66A4-4d5d-A282-EA4FE481EE40"

    Public Sub New()
        MyBase.New()
    End Sub

    Public Function myFunction() As Integer
        Return 42
    End Function

    Private Const INTERFACESAFE_FOR_UNTRUSTED_CALLER As Integer = &H1
    Private Const INTERFACESAFE_FOR_UNTRUSTED_DATA As Integer = &H2

    Public Function GetInterfaceSafetyOptions(ByRef iid As Guid, ByRef pdwSupportedOptions As Integer, ByRef pdwEnabledOptions As Integer) As Integer Implements IObjectSafety.GetInterfaceSafetyOptions
        pdwSupportedOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER Or INTERFACESAFE_FOR_UNTRUSTED_DATA
        pdwEnabledOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER Or INTERFACESAFE_FOR_UNTRUSTED_DATA
        Return 0
    End Function

    Public Function SetInterfaceSafetyOptions(ByRef iid As Guid, ByVal dwOptionSetMask As Integer, ByVal dwEnabledOptions As Integer) As Integer Implements IObjectSafety.SetInterfaceSafetyOptions
        Return 0
    End Function

End Class

Here is sample code for running it in IE:

Code:

<head>
<script language="javascript">
<!-- hide me from other browsers
function showanswer() {
   var a = myControl.myFunction();
   alert("The answer is "+a);
}
// end hiding from other browsers -->
</script>
</head>
<body>
<object id="myControl"
classid=clsid:6DB79AF2-F661-44AC-8458-62B06BFDD9E4>
</object>
<h1>Click below for an answer!</h1>
<input type="button" name="answerbutton" value="Click Me!" onClick="showanswer()">
</body>
</html>

The first time you click the 'Click Me' button in IE, the function call works. Click the button a second time, and it fails.

Can anyone point me to solving this?

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