public interface IQuoteClient {
  String getQuote();
  Boolean setQuote(String quote);
}

public class QuoteClient : IQuoteClient {
  // COM requires a parameterless constructor
  public QuoteClient() { ; }
  public string getQuote() { return String.Format"quote";}
  public bool setQuote(string quote) { return true; }
}

Go the project Properties and check the “Make assembly COM-Visible” box which you find in the Application tab, Assembly Information. Then you go to the Build tab and check “Register for COM interop” box and at the Signing tab you check the “Sign the assembly” box and assign a key. Build the project.

Now we have to extract a typelibrary, register the typelibrary and install it in the global assembly cache. Open a Visual Studio 2005 Command Prompt and go to your project\bin\Debug directory. Type the following commands:

tlbexp QuoteClient.dll
regasm QuoteClient.dll /tlb:QuoteClient.tlb
gacutil /i QuoteClient.dll

Now you can import the classes in this assembly from your WIN32 application as following:

#import "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorlib.tlb"
#import "D:\projects\Test\QuoteClient\bin\Debug\ClientLibrary.tlb" no_namespace named_guids

And you can use them just like any other COM component:

CoInitialize(NULL);

IQuoteClient *qc = NULL;
HRESULT hr = CoCreateInstance(
  CLSID_QuoteClient, 
  NULL, 
  CLSCTX_INPROC_SERVER, 
  IID_IQuoteClient, 
  reinterpret_cast<void**>(&qc)
);

if (SUCCEEDED(hr)) {
  cout << "Quote: " << qc->getQuote() << endl;
  qc->Release();
  qc = NULL;
}

CoUninitialize();

[DllImport("kernel32", SetLastError=true)]
extern int GetPrivateProfileString(
  String ^pSection, 
  String ^pKey, 
  String ^pDefault, 
  StringBuilder ^pValue, 
  int pBufferLen, 
  String ^pFile
);

StringBuilder ^buf = gcnew StringBuilder(256);
GetPrivateProfileString(
  "logsection", 
  "file", 
  "default", 
  buf, 
  buf->Capacity, 
  "example.ini"
);

std::string _log_file = new string(
  (char*) Marshal::StringToHGlobalAnsi(logf).ToPointer()
);

typedef struct {
  char name[9];
  int name;
  double sterr;
} TEST;

FileStream ^f = gcnew FileStream("C:\\TEST.DAT", FileMode::Open, FileAccess::ReadWrite);
BinaryReader ^r = gcnew BinaryReader(f);
array<Byte> ^buf = r->ReadBytes(sizeof(TEST));
TEST test;
Marshal::Copy(buf, 0, (IntPtr) &test, sizeof(TEST));

#include <iostream>
using namespace std;

void customcallback() {
        cout << "running custom callback" << endl;
}

typedef int (*method)(int, int);

int sum(int a, int b) {
        return a + b;
}

method dosum() {
        return &sum;
}

int main() {
        void (*plugin)() = NULL;
        plugin = &customcallback;
        plugin();

        method mymethod = dosum();
        cout << mymethod(10, 4) << endl;

        return 0;
}