How do I return an array/list/collection of objects from C# to VB6

Question

I am creating a COM Visible C# object to proxy calls to a webservice for VB6 application. I have a method that returns an array of objects.

public DocActionReport[] DocActionReportByDateRange(System.DateTime reportStartDate, System.DateTime reportEndDate)
    {
        object[] results = this.Invoke("DocActionReportByDateRange", new object[] {
                    reportStartDate,
                    reportEndDate});
        return ((DocActionReport[])(results[0]));
    }

When I call this method via VB6, like so:

Dim proxy As New QueueMovementServiceClient.ReadQueueInfo
Dim report() As QueueMovementServiceClient.DocActionReport

report = proxy.DocActionReportByDateRange(startDate, reportEndDate)

It successfully executes (I can see that via logging on the web service) but no data is returned to the object in VB6 (LBound(report) == 0, UBound(report) == -1).

I have tried a couple of different approaches (changing the method to a void method and passing the collection in as a ref parameter) but no joy so far.

What do I need to do to return an array of objects (list, collection, whatever) to a VB6 consumer?

Answer 1

When calling a WebService all results must by serialized in order to travel through HTTP.

I recommend you to return JSON or XML to make the WebService more interoperable with other platforms.