Access a function present in C# dll using Python

Question

I want to access a function my_function() present in a c# file which is compiled into a .net dll - abc.dll.

C# file

            using System;
            using System.Collections.Generic;
            using System.Linq;
            using System.Text;
            using System.Threading.Tasks;


            namespace Test
            {
                public class Class1
                {
                    public string my_function()
                    {
                        return "Hello World.. :-";
                    }
                }
            }

After compiling the above code to abc.dll

Using the below python trying to access my_function()

            import ctypes
            lib = ctypes.WinDLL('abc.dll')
            print lib.my_function()

Above code throws error

lib.my_function() Traceback (most recent call last): File "", line 1, in File "C:\Anaconda\lib\ctypes__init__.py", line 378, in getattr func = self.getitem(name) File "C:\Anaconda\lib\ctypes__init__.py", line 383, in getitem func = self._FuncPtr((name_or_ordinal, self)) AttributeError: function 'my_function' not found

I'm guessing you should use the full function's namespace. Did you try print lib.Test.Class1.my_function() ? — Matias Cicero
– Matias Cicero, Commented Jul 25, 2016 at 13:47

Anon Coward · Accepted Answer · 2016-07-25 13:55:48Z

2

You haven't made the function visible in the DLL.

There are a few different ways you can do this. The easiest is probably to use the unmanagedexports package. It allows you to call C# functions directly like normal C functions by decorating your function with [DllExport] attribute, like P/Invoke's DllImport. It uses part of the subsystem meant to make C++/CLI mixed managed libraries work.

C# code

class Example
{
     [DllExport("ExampleFunction", CallingConvention = CallingConvention.StdCall)]
     public static int ExampleFunction(int a, int b)
     {
         return a + b;
     } 
}

Python

import ctypes
lib = ctypes.WinDLL('example.dll')
print lib.ExampleFunction(12, 34)

answered Jul 25, 2016 at 13:55

Anon Coward

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4 Comments

Vinay Ranjan Over a year ago

Do I need to include and namespace for this, because even after including the DLLExport package getting error - The type or namespace name 'DLLExport' could not be found.

Anon Coward Over a year ago

You'll need to install the Unmanaged Exports package, either from the website I linked, or by finding the NuGet package under 'Project', then 'Manage NuGet Packages...'

Vinay Ranjan Over a year ago

Its still showing the same error - AttributeError: function 'ExampleFunction' not found

David Heffernan Over a year ago

Then you are doing something wrong. But that's now your problem to debug.

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