Subscribe to C# .net Event in VB6

Question

I need to get be able to handle a .net event in VB6. So far i have it set up by making me c# class COM visible. My VB6 object can call methods on it fine but now i need some way to communicate from .net to VB. If i add an event to my c# class the .net wrapper seems to add an add_EventName and remove_EventName which i assume this is to subscribe and unsubscribe to the event. But i'm still a novice when it comes to VB6 and come so i'm not really sure how to use it.

The add_EventName seems to take an EventNameEventHadler but what do i give it? i tried the sub but this gives me a runtime error. Anyone know how to use this? Here is an example of what i have

Private oHost As HostService.IHost

Private Sub Form_Load()
    Set oHost = New HostService.Host
    oHost.Start
    oHost.add_EvalReceived EvalReceivedEventHandler
End Sub

Private Sub EvalReceivedEventHandler(ByVal sender As Variant, ByVal e As EvalReceivedEventArgs)
MsgBox "Eval Received in VB: " & e.Eval.TimeSent & ":" & e.Eval.FirstName & " " & e.Eval.LastName & " - " & e.Eval.Comments
End Sub

So oHost.add_EvalReceived line is wrong

Answer 1

You could try adding WithEvents to your declaration of oHost

Private WithEvents oHost As HostService.IHost

Then the IDE should allow you to create event handlers on oHost. It's just like making your Form_Load event handler. The drop-down at the top-left of the code window should let you select oHost.

Disclaimer: I've used this many times to handle events from COM objects. I've never actually tried handling events from a .Net object through interop, but I would think you must do it like this.

Answer 2

Ok i got it working with help from MarkJ. I had to have an interface that represents my events for COM. So they ended up looking like this

[ComSourceInterfaces(typeof(IHostEvents))]
[ClassInterface(ClassInterfaceType.None)]
[Guid("037CF765-4C30-4CF7-969C-1775E79844CE")]
public class Host : IHost
{
    //IHost implementation
}

[ComVisible(true)]
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
[Guid("8C0C3F0E-5793-4E11-AB20-3A556C0B6790")]
public interface IHostEvents
{
    [DispId(1)]
    void EvalReceived(object sender, EvalReceivedEventArgs e);
}

Answer 3

In VB6 you can use the AddressOf operator to create the delegate implicitly:

oHost.add_EvalReceived AddressOf EvalReceivedEventHandler