Flutter FFI Failed to lookup symbol The specified procedure could not be found

Question

i'm trying to integrate a native c++ library .dll to my flutter desktop app

this is the code from header and cpp (it contain different function but i'm trying to achieve this with a simple hello function)

the header file:

#pragma once

#include <msclr/marshal_cppstd.h>
#pragma managed(push, off)
#include "lz4/lz4frame.h"
#include "fastlz.h"
#pragma managed(pop)

using namespace System;
using namespace System::Collections::Generic;

namespace LSLib {
    namespace Native {
        public ref class LZ4FrameCompressor abstract sealed
        {
        public:
            static void hello();
        };
    }
}

the c++ file:

#pragma once

#include "lz4wrapper.h"
#include <string>
#include <iostream>

namespace LSLib {
    namespace Native {
        void LZ4FrameCompressor::hello() {
            std::string strMytestString("hello world");
            std::cout << strMytestString;
        }
    }
}

and this is the code from flutter

final path = absolute(r'native\LSLibNative.dll');
final library = DynamicLibrary.open(path);
final void Function() func = library .lookup<NativeFunction<Void Function()>>('hello').asFunction();
func();

and i'm getting this error:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Invalid argument(s): Failed to lookup symbol 'hello': The specified procedure could not be found.

 (error code: 127)
#0      DynamicLibrary.lookup (dart:ffi-patch/ffi_dynamic_library_patch.dart:33:70)
#1      LS4Service.initialize (package:bg3_mod_translator/src/infrastructure/ls4_service.dart:22:43)
#2      TranslateComponent.initialize (package:bg3_mod_translator/src/infrastructure/translate_component.dart:50:18)
<asynchronous suspension>
#3      main (package:bg3_mod_translator/main.dart:51:3)
<asynchronous suspension>

i'm not an expert of c++ but i can't undestart what i'm doing wrong any help? thanks!