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Consuming Python COM Server from .NET

on Thu Dec 14, 2017 3:29 pm
I wanted to implement python com server using win32com extensions. Then consume the server from within the .NET. I used the following example to implement the com server and it runs without a problem but when I try to consume it using C# I got FileNotFoundException with the following message "Retrieving the COM class factory for component with CLSID {676E38A6-7FA7-4BFF-9179-AE959734DEBB} failed due to the following error: 8007007e." . I posted the C# code as well.I wonder if I'm missing something I would appreciate any help.

Thanks, Sarah
Code:
#PythonCOMServer.py

import pythoncom
class PythonUtilities:
    _public_methods_ = [ 'SplitString' ]
    _reg_progid_ = "PythonDemos.Utilities"
    # NEVER copy the following ID

    # Use"print pythoncom.CreateGuid()" to make a new one.
    _reg_clsid_ = pythoncom.CreateGuid()
    print _reg_clsid_
    def SplitString(self, val, item=None):
        import string
        if item != None: item = str(item)
        return string.split(str(val), item)

# Add code so that when this script is run by
# Python.exe,.it self-registers.

if __name__=='__main__':       
    print 'Registering Com Server'
    import win32com.server.register
    win32com.server.register.UseCommandLine(PythonUtilities)


// the C# code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {

              Type pythonServer;
              object pythonObject;
              pythonServer = Type.GetTypeFromProgID("PythonDemos.Utilities");
              pythonObject = Activator.CreateInstance(pythonServer);

        }
    }
}

Answers

A COM server is just a piece of software (a DLL or an executable) that will accept remote procedure calls (RPC) through a defined protocol. Part of the protocol says that the server must have a unique ID, stored in the Windows' registry. In our case, this means that you have "registered" a server that is not existing. Thus the error (component not found).

So, it should be something like this (as usual, this is untested code!):
Code:
import pythoncom

class HelloWorld:
    _reg_clsctx_ = pythoncom.CLSCTX_LOCAL_SERVER
    _reg_clsid_ = "{B83DD222-7750-413D-A9AD-01B37021B24B}"
    _reg_desc_ = "Python Test COM Server"
    _reg_progid_ = "Python.TestServer"
    _public_methods_ = ['Hello']
    _public_attrs_ = ['softspace', 'noCalls']
    _readonly_attrs_ = ['noCalls']

    def __init__(self):
        self.softspace = 1
        self.noCalls = 0

    def Hello(self, who):
        self.noCalls = self.noCalls + 1
        # insert "softspace" number of spaces
        return "Hello" + " " * self.softspace + str(who)

if __name__ == '__main__':
    if '--register' in sys.argv[1:]  or '--unregister' in sys.argv[1:]:
        import win32com.server.register
        win32com.server.register.UseCommandLine(HelloWorld)
    else:
        # start the server.
        from win32com.server import localserver
        localserver.serve('B83DD222-7750-413D-A9AD-01B37021B24B')
Then you should run from the command line (assuming the script is called HelloWorldCOM.py):
Code:
HelloWorldCOM.py --register
HelloWorldCOM.py
Class HelloWorld is the actual implementation of the server. It expose one method (Hello) and a couple of attributes, one of the two is read-only. With the first command, you register the server; with the second one, you run it and then it becomes available to usage from other applications.
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