Question

I need to pass an empty Array of Variants to a DLL written in C (and available on all Windows versions), and the C code (which I have no control over and cannot edit) will populate the Empty Array of Variants with its some return values.

Bascially, when I try this – the ByRef Array is always empty when it should contain the results of the function/sub call (if I do the exact same thing in .NET, it works).

I’m thinking I need to do a custom declaration so VB knows how to call the C function, or?

Here is how the C sub/function is declared. Given this, what do I need to do in order to ensure C is able to use my Empty Array properly and I in tern get my results back?

HRESULT InvokeAction(
  [in]       BSTR bstrActionName,
  [in]       VARIANT varInActionArgs,
  [in, out]  VARIANT *pvarOutActionArgs,
  [in, out]  VARIANT *pvarRetVal
);

More information about this function: http://msdn.microsoft.com/en-us/library/aa382237(VS.85).aspx

Thanks

Answer 1

From http://msdn.microsoft.com/en-us/library/aa381230(VS.85).aspx:

Dim returnVal
Dim outArgs(1)
Dim args(1)
args(0) = 3
returnVal = service.InvokeAction("GetTrackInfo", args, outArgs)
'return Val now contains the track length
'and outArgs(0) contains the track title
Dim emptyArgs(0)
returnVal = service.InvokeAction("Play", emptyArgs, emptyArgs)
'returnVal indicates if the action was successful

Just how you get and instance of service is not clear from this example though.