Remote control using DCOM: Error: "ActiveX component cannot be created."

Question

Hello,
I want to address a OMICRON CPC100 device via remote control. I have a dll ("TESTCONTROL.dll"), which provides methods to control the CPC100. In order to encapsulate this functionality, I've written a VB.NET-dll ("CLC_CL_for_Net.dll") (it's a class-dll) which calls methods of TESTCONTROL.dll. Now I want to use CLC_CL_for_Net.dll in LabVIEW.
Here's the code of CLC_CL_for_Net.dll:
Imports TESTCONTROLLib
Namespace MyCPCNamespace
    Public Class CPCClass
        Public Sub New()
        End Sub
        Public Sub testfunction(ByVal ipaddress As String)
            Dim tc As TestProcedure
            Dim atm As IATMTest
            tc = CreateObject("TestControl.TestProcedure", ipaddress)   '<-- here the error occurs!
            atm = CreateObject("TestControl.ATMTest", ipaddress)
            atm.Activate(300, 10, 1)
            atm.Deactivate()
        End Sub
    End Class
End Namespace
In order to enable DCOM on my computer, I did the following:
- I switched the firewall off.
- I started "dcomcnfg.exe", chose "Component Services/Computers/My Computer -> Properties" and checked the checkbox "Enable Distributed COM on this computer".
- I also chose the tab "My Computer Properties/COM Security" and allowed everyone full access and launch
permissions.
- I created an exe-file from my LabVIEW VI, which uses the dll, with the help of the LabVIEW Application Builder.
For this exe-file and also for the TESTCONTROL, I set the authentication level to "None".
For test purposes, I used my dll in a C++ project. There everything works fine. However, when I try to use the dll
in LabVIEW (using LabVIEW's .NET constructor node and method node, which you can find under Connectivity -> .NET), the program fails at the line "tc = CreateObject("TestControl.TestProcedure", ipAddress)".
Here the error message displayed by LabVIEW (I translated it from German into English):
"Error 1172 has occurred at Error calling method CLC_CL_for_Net.MyCPCNamespace.CPCClass.testfunction of ObjectId
handle: 0x2BB117C for obj 0x3F19E1D[CLC_CL_for_Net.MyCPCNamespace.CPCClass] in domain [LabVIEW Domain for Run] and
thread 3792, (System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 Inner Exception: System.Exception: The ActiveX component cannot be created.
) in CPC100_RemoteControlVI.vi"
As the dll works when I use it in the C++ project, I don't understand why this error occurs when I use the dll in
LabVIEW. Do I have to give LabVIEW any special permissions?
Can anyone help me to solve this problem? Thanks a lot for your efforts!
Regards,
Matthias

Answer 1

Hi Matthias,
I am not really familiar with .NET assemblies but I found couple informations on your error :
First of all, about the Error 1172 in LabVIEW, there is two things to proof:
Ensure that the .NET assemblies that you are using are saved in the root directory of the top-level VI.
Add the .NET assembly as a reference in LabVIEW by selecting Tools»Advanced»NET Assembly References. Click the Add button and navigate to the location of all the assemblies that you want to call.
Those two steps sometimes solve Error 1172 related problems. I also found some information about the "ActiveX component cannot be created" error. A .Net Class library needs to be in a COM wrapper in order for it to be called through COM methods, such as ActiveX. The way to do so is:
1. Create a new .NET Class Library project.
2. Remove the Class1.vb that is created.
3. Click Add Class on your project.
4. Choose "COM Class", and add it.
5. Add at least 1 function or sub in it.
6. Compile it, and Visual Studio should registrer it automaticly.
If you whish to manuall reg it, or create a registry entry file, use "RegAsm.exe" in the .NET Framework folder.
I hope this could be any helpful to you
Regards
Florian Abry
Application Engineer Group Leader
NI Germany