Ironpython - Issues attaching to an instance of an already running program

Question

Ok folks this is a long one, so please bear with me. I'll preface this by stating that I am -for all intents and purposes- a noob.

I'm trying to link to a running instance of a program (ETABS) using IronPython. The program has an API and decent documentation on how one can go about hooking into the running instance (EXAMPLE). However, their examples are for Python, C#, VB.net but not IronPython.

No biggie I thought, the Marshal module can be used to hook into it. So I tried this:

from System.Runtime.InteropServices import Marshal
csiApp = Marshal.GetActiveObject("CSI.ETABS.API.ETABSObject") 
SapModel=csiApp.SapModel

Unfortunately I get errors on that last line - "ETABSObject has no attribute SapModel".

And yes, I've tried running it with csiApp.SapModel() as well with the same results.

So I delved deeper into it and apparently the object needs to be cast into another type - at least that's the way its been done for the C# example (LINK). Since - to my knowledge - we can't really cast objects around in Python (and yes, I've already tried clr.Convert) I came to the conclusion that the object being returned to Ironpython is a few abstractions removed from the object that I really need. Apparently comtypes can handle this automatically in the background (seeing as the python example works flawlessly). The code block below shows the object types returned to Ironpython and to pure python respectively:

Ipy : <System.MarshalByRefObject object at 0x000000000000002B [CSI.ETABS.API.ETABSObject]>

Python with comtypes : <POINTER(cOAPI) ptr=0x2e68d17f7c8 at 2e690b36a48>

I'm working on Ironpython 2.7.3 and can't really update it (for several reasons not relevant to this post). Would love to have advice on how to fix this or on how to install comtypes on Ipy.

Andorrax · Accepted Answer · 2019-06-17 00:49:16Z

0

So I think I've found the reason why this is happening - Ironpython cannot directly use MarshalByRefObjects (source) since Reflection doesn't work on these. It seems I'll need to create a C# class which can cast this object into the one I want, compile it into a dll and load that into my Ipy code.

I'll leave this here in case someone with more knowledge has a better answer.

answered Jun 17, 2019 at 0:49

Andorrax

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