How do I call LabVIEW's ActiveX interface from .NET?

[unDees]

I'm trying to call a LabVIEW VI from C# using LabVIEW's ActiveX interface. I've successfully imported LabVIEW.tlb and can do a few simple things like load a VI into memory and run it.

But things get more complicated when I need to use a cluster output from one VI as the input to another. The return value of GetControlValue is, unfortunately, a System.Object refnum. This is useless for passing into LabVIEW: it's just a pointer.

How to I get C# to pass the System.Object refnum in as a Variant containing the actual cluster data instead of a Variant containing a 32-bit pointer? I'd even settle for flattening the C# object to some kind of string, but the ToString() method is useless: it returns "System.Object[]" ins
tead of an actual representation of the data.

[BeckyB]

Hello -

I'm not familiar with C# commands, but I can point you to some useful information on LabVIEW and ActiveX:

You can obtain a description of all the methods and properties in the LabVIEW help. In LabVIEW 7.0 you should open help (Help >> VI, Function, & How-To Help). From the contents tab select Windows Connectivity >> ActiveX >> Properties & Methods. Here you will find information on the properties and methods that LabVIEW makes available.

This tutorial is a great introduction to LabVIEW and ActiveX.

I've also attached an example (written in LabWindows/CVI) which demonstrates how to use the LabVIEW ActiveX Automation interface to la
unch and run a LabVIEW VI. In this application the LabWindows/CVI example acts as the Automation Client to control LabVIEW through LabVIEW's Automation Server.

Good luck with your project and have a great day!

Becky B.
Applications Engineer
National Instruments