.NET Test Stand API and interop with CVI

[Phlamb]

I'm working with the Test Stand API in .NET and trying to call some legacy code written in CVI and I've hit a wall.

One of the functions I'm calling has a CAObjHandle parameter that is being used to retrieve test limits:

TS_PropertyGetValNumber (limitsHandle, NULL, "Limits.High" , 0, &highLimit);

I've created a PropertyObject in .NET containing these values, but when I try to call the native function passing a reference to the PropertyObject directly calling TS_PropertyGetValNumber results in an error.

[DllImport("5042200.dll", CallingConvention = CallingConvention.StdCall)]

        public static extern void Initialize(ref int result, StringBuilder reportText,

            ref short errorOccurred, ref long errorCode, StringBuilder errorMessage);

[DllImport("LegacyTest.dll", CallingConvention = CallingConvention.StdCall)]

public static extern void power_up([MarshalAs(UnmanagedType.LPArray, SizeConst = 10)] double[] measurements,

                                            ref PropertyObject limitsHandle);

PropertyObject po =BuildLimitsPropertyObject();

power_up(meas, ref po);

Has anyone here been successful with this or something similar?  Any ideas on what to try next?

[Erik_Crank · Accepted solution]

A CVI CAObjHandle is an integer that is a handle to a COM interface pointer. You cannot automatically convert a .NET COM pointer to a CAObjHandle using COM interop. I would first consider rewriting the CVI code in .NET. If that's not an option, you could try calling the CVI function CA_CreateObjHandleFromInterface to create the handle and then use CA_DiscardObjHandle to release it after the function call. Both of these functions are in cviauto.dll.

[Phlamb]

Thanks, calling CA_CreateObjHandleFromIDispatch and passing in the .NET PropertyObject worked perfectly.