Creating a dll in C# and calling it from VC6
============================================

1) Using VS2005 create a C# dll.

2)

3) Add the follwing code to the dll's namespace:

	// Since the .NET Framework interface and coclass have to behave as
    // COM objects, we have to give them guids.	And, we have to expose
	// them via an attribute.
    [ComVisible(true)]
    [Guid("DBE0E8C4-1C61-41f3-B6A4-4E2F353D3D05")]
    public interface ISharpServicesInterface
    {
        int ShowMessage(string sData);
    }

    [ComVisible(true)]
    [Guid("C6659361-1625-4746-931C-36014B146679")]
    public class ISharpServicesInterfaceImplementation : ISharpServicesInterface
    {
        public int ShowMessage(string s)
        {
            string ss = string.Format("Hello {0} ", s);
            System.Windows.Forms.MessageBox.Show(ss);
            return 100;
        }
    }
4) Build the solution the execute the following on the command line:
   Regasm /codebase /tlb c:\tmp\sharp\bin\debug\sharp.dll	
   
   You'll have to adjust the path and name to suit. This fills in the 
   appropriate registry GUID entrys.
			
	
5) Using Visual Studio V6 create dialog based project.

6) Add a button, label it 'Call C#DLL', and in its handler add the following code:

	ISharpServicesInterface *cpi = NULL;
	int retval = 1;

	// Initialize COM and create an instance of the InterfaceImplementation class:
	CoInitialize(NULL);
	HRESULT hr = CoCreateInstance(CLSID_ISharpServicesInterfaceImplementation,
               NULL, CLSCTX_INPROC_SERVER,
               IID_ISharpServicesInterface, reinterpret_cast<void**>(&cpi));

	if (FAILED(hr))
	{
		printf("Couldn't create the instance!... 0x%x\n", hr);
	}
	else
	{
		printf("Calling function.\n");
		fflush(stdout);
		
		if( cpi->ShowMessage("Darren") == 100 )
			retval = 0;
        printf("Returned from function.\n");
	}

	cpi->Release();
	cpi = NULL;

   // Be a good citizen and clean up COM:
   CoUninitialize();	

7) In the header somwhere you'll need to add the following:
	#include <objbase.h>
	/*
	Adjust path to suit. This will create temp files with the required CLSID
	and IIDs needed to query COM.
	*/
	#import "c:\tmp\sharp\bin\debug\sharp.tlb" no_namespace named_guids