How to use a c#.net dll in vc++6 programmes?

  I am trying to figure out if it is possible to use a c#.net dll in vc++6 programmes. So far i have created a dll, a tlb using the tlbexp.exe and a RES file using the rc.exe. I managed to import the tlb file in a c++ program but i cannot use any  of my c# class methods.
Is it possible to use c#.net code in vc++6 and if yes how can i do that?
For instance what do i need to do in order to use these classes in vc++6:

using System;

namespace Operations
{
      public class Addition
      {
            public Addition()
            {                  
            }
            public double Add(double sum1, double sum2)
            {
                  return sum1 + sum2;
            }
      }
      
      public class Multiplication
      {
            public Multiplication()
            {                  
            }
            public static double Multiply(double multiplier, double multiplicand)
            {
                  return multiplier*multiplicand;
            }
      }
}
CeletronAsked:
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bluedaisydawgConnect With a Mentor Commented:
It looks ok - when you step through p is still set to nothing after the CreateInstance though right?  Try

p.CreateInstance(__uuidof(Operations.Addition)

see if that helps.


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smeggheadCommented:
have you tried calling RegAsm ??

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bluedaisydawgCommented:
I'm having a similar problem.  This is what I did:

- Make sure you are compiling the DLL with the Com interop flag set to true (right click on the solution, pick properties, Configuration properties, build)

- Then I did this: http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B815808

- Add this to your C++ file:
#import "PATH\DLLNAME.tlb"
using namespace DLLNAMESPACE;

You'll then be able to see all your stuff from C++.

 
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bluedaisydawgCommented:
Also in your C# you need to have something like this:

namespace MyNamespace
{
      /// <summary>
      /// Summary description for Class1.
      /// </summary>
      public interface IManagedInterface
      {
              bool myFunction(string spName, string connectionString);
      }

      public class Class1:IManagedInterface
      {
                         public bool myFunction(string spName, string connectionString)
                        {
                                // function stuff here
                         }


From C++ do this:

      ::CoInitialize(NULL);


      _Class1Ptr p;

      p.CreateInstance("Mynamespace.Class1");


      IManagedInterfacePtr t = p.GetInterfacePtr();

      t->executeStoredProcedure("test", "test");


      CoUninitialize();


Put those two comments together and it should work just fine.  I just this minute got this working myself.
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CeletronAuthor Commented:
I did what you said bluedaisydawg and i can see now my class methods but when i am running the program i always get an exception:

Debug Error!

Program: program path

Abnormal program termination

That happens when the program reaches the following line:
 t->executeStoredProcedure("test", "test");
or :
a = t->Add(1, 1);      in my code

The problem seems to be the interface which is never implemented and in fact remains NULL during the whole process. From what i understand the "p.CreateInstance("Operations.Addition");" fails to create the instance, and when the program tries to excecute the "t->Add(1, 1)" it crashes cos it doesn't know what to do with it...

i am posting my code in case i did something wrong and i cannot see it...

//
//   C#.NET code
//

using System;

namespace Operations
{
      public interface IManagedInterface
      {
            double Add(double sum1, double sum2);
      }

      public class Addition:IManagedInterface
      {
            public Addition()
            {                  
            }

            public double Add(double sum1, double sum2)
            {
                  return sum1 + sum2;
            }
      }
      
}

//
//   VC++6 code
//
#include "stdafx.h"
#import  "Operations.tlb"

using namespace Operations;

int main(int argc, char* argv[])
{
      double a = 0;
      ::CoInitialize(NULL);

      _AdditionPtr p;

      p.CreateInstance("Operations.Addition");

      IManagedInterfacePtr t = p.GetInterfacePtr();


      a = t->Add(1, 1);     // It crashes here...

      CoUninitialize();

      printf("%d", a);
      getchar();
      return 0;
}

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CeletronAuthor Commented:
Nope... p is still NULL... Does it work at your pc?
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bluedaisydawgCommented:
yes - the one i have is working...  try this:

go to Programs->Microsoft Visual Studio .NET -> Visual Studio.NET tools ->Visual Studio .NET Command Prompt

Then type

regasm PATH\LIBNAME.dll

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CeletronAuthor Commented:
Ok it worked. In fact it should work before as well but instead of having
p.CreateInstance(__uuidof(Addition));
i had
p.CreateInstance(__uuidof(_Addition)); ....

Thx for the help bluedaisydawg.

By the way, do you know if it is possible to use c#.net static methods as well???
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