Using UnmanagedExports Framework in Unity

Question

I try to use UnmanagedExports in my Unity project since I have one function which I would like to call from a Python program. I get the following error when I try to call the function in my Python script:

AttributeError: function 'ConvertRawToBinData' not found

Like mentioned here, I tried to build the project via x64 target. When I change the target to x64 in Visual Studio I cannot import my libraries:

The type or namespace name 'type/namespace' could not be found

Can I use UnmanagedExports in a Unity project and if yes, how?

Here is the C# code:

using RGiesecke.DllExport;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace ConverterAPI
{
    public class ConverterAPI
    {
        [DllExport("ConvertRawToBinData", CallingConvention = CallingConvention.StdCall)]
        public static void ConvertRawToBinData(string settingsPath, string collectionSettingsPath, string rawDataPath)
        {
            Settings settings = Util.ImportJson<Settings>(settingsPath);
            CollectionSettings CollectionSettings = Util.ImportJson<CollectionSettings>(collectionSettingsPath);

            Converter.Convert(settings, CollectionSettings, rawDataPath);
        }
    }
}

Here is the Python code:

import ctypes
import os
from pathlib import Path, PurePath

apiPath = PurePath(assetsPath.parent, 'Build', 'Target', 'API.dll')
converterAPI = ctypes.cdll.LoadLibrary(str(apiPath))
converterAPI.ConvertRawToBinData("", "", "")