A Simple C# Dll - How to Call It from Excel, Access, Vba, Vb6

A Simple C# DLL - how do I call it from Excel, Access, VBA, VB6?

You can't access a static member via COM interop. In fact your code doesn't even compile, the method should be in a class. Here is how you can do it:

[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("01A31113-9353-44cc-A1F4-C6F1210E4B30")]  //Allocate your own GUID
public interface _Test
{
    string HelloWorld { get; }
}

[ClassInterface(ClassInterfaceType.None)]
[Guid("E2F07CD4-CE73-4102-B35D-119362624C47")]  //Allocate your own GUID
[ProgId("TestDll.Test")]
public class Test : _Test
{
    public string HelloWorld { get { return "Hello, World! "; } }
}

The project properties Build tab, select Register for COM interop. So you can see the results quickly. To install the dll on another machine you need to use regasm.

To then consume this:

Dim o : Set o = CreateObject("TestDll.Test")
MsgBox o.HelloWorld

You can also reference the dll and use early binding:

Dim o As TestDll.Test
Set o = New TestDll.Text
MsgBox o.HelloWorld

Calling a VB6 method from a .NET DLL

As VB6 creates COM DLLs, Visual Studio should have no problems generating an interop stub for you. Simply add a reference to the VB6 DLL from your .NET project by selecting Add Reference in Visual Studio and finding your DLL under the COM tab. Make sure the VB6 DLL is registered on your machine before you do this.

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