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ActiveX and C# Interop

P: n/a
I am having problems getting an ActiveX DLL written in VB6 to call a
method in a C# class library component.

My C# DLL is called CSharpProject.dll and contains a public class
called CSharpClass. In this class is a single public method that
returns the string "Hello

from C sharp".

My VB6 ActiveX DLL references the C# DLL (CSharpProject.dll) using the
type library CSharpProject.tlb. The ActiveX DLL contains two methods,
the first just

returns a string declared within the method, and the second tries to
call the method defined in the C# component.

I then have a simple ASP.Net webform (Webform1.aspx) that creates an
instance of the ActiveX object using client side Javascript.

Everything works fine on my local machine but when I try using it on
another machine I get the following error(s):

1) "File or assembly name CSharpProject, or one of its dependancies,
was not found"

I have tried the following things to resolve the problem:

C# Component:

* I have created the tlb file for the CSharpProject.dll

1) automatically using the setting in Visual Studio "Register for COM
Interop" set to true.
2) using the .net tool tlbexp
3) using regasm /tlb option

(I have also ensured that the .tlb file is registered on other
machines using a tool called Reggie.exe.)

* I have tried creating a strong name for the component and
registering it in the GAC but this doesn't solve the problem.

VB6 ActiveX DLL:

* I have referenced the tlb as per a normal reference.

The code is as follows:

Public Function method1() As String
On Error GoTo fail
foo = "dave"
Exit Function
foo = "Error in foo occurred in VB ActiveX DLL (" & Err.Description
& ")"
End Function

Public Function method2() As String
On Error GoTo fail
Dim objCSharp As New CSharpProject.CSharpClass
Dim tmp As String
tmp =
method2 = tmp
Exit Function
method2 = "Error occurred in VB ActiveX DLL (" & Err.Description &
End Function

NOte: I have also tried using the following code to declare and
instantiate the C# class -

Dim objCSharp
Set objCSharp = CreateObject("CSharpProject.CSharpClass")

However this returns the following error message from the VB6 ActiveX
DLL: "Object doesn't support this property or method."


var obj = new ActiveXObject("VBActiveXDLL.VBClass1");

All works fine on my local machine but when I copy/register/install
all the components on another machine (which has Visual Studio.Net and
v6 installed) it

doesn't work.

Any suggestions, comments, or ideas would be much appreciated

Jul 21 '05 #1
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