如何在DLL项目中的C ++中创建名称空间和构造函数？

Question

I created on my visual studio 2012 pro a new dll project and the main .cpp file is empty except this line:

#include "stdafx.h"

In this dll project I have a new c language item(module) I added with some functions inside.

In fact I want to create in my main .cpp file some functions that will call the function from the c item(module).

For example in the .cpp file I will have something like this:

void start()

{

   encoder.start();

}

Then in the .cpp I need to add a constructor so I can call there the start()

How should I do it ?

Here is an example in my solution i have two projects one console application one dll. This is the content of the main cpp file from the console application project:

#include "stdafx.h"
#include "targetver.h"

extern "C" {
    void  video_encode_example(const char *filename);
}


int _tmain(int argc, _TCHAR* argv[])
{

    video_encode_example("adi.avi");
    return 0;
}

vide_encode_example is a function from this c item(file/module) i created in the console application project. I have a file called example.c and the video_encode_example is in the example.c

Now i added to the solution a new dll project and the main.cpp file is empty except the line: #include "stdafx.h"

What i want to do in this dll project in the main.cpp is two things:

1. To create some function for example

   void thisstart() { }

Then i want to in this start function to call a start() function which is in ac file/module i created in the dll project.

So it should look like:

void thisstart()
  {
    start();
  }

Where start(); is from the c module/file

Then i'm going to use this dll in c# and in c# i want to be able to use the thisstart() function.

EDIT

This is the main.h content:

namespace dllproj{

    extern "C" void start();
    void thisstart();
}

I'm getting and two errors now on dllproj:

1. Error 2 error C2054: expected '(' to follow 'namespace'
2. 4 IntelliSense: expected an identifier

Then this is the cpp file content now:

#define dllproj;

#include "stdafx.h"
#include "targetver.h"
#include "main.h"

void thisstart()
 {
     dllproj;::start();
 }

And i'm getting two errors:

1. on the define line: Error 1 error C2008: ';' : unexpected in macro definition
2. on the dllproj;::start(); Error 3 error C2143: syntax error : missing ';' before ':'

Please show me the complete solution and explain to me also which variable later in CSHARP i will use with the dll to make an instance for it and to call this function/s in the cpp ?

In csharp for example when i add the dll : test = new something(); then test.thisstart();

Answer 1

From the comments "start() is in the dll project in a (c language file i create test.c)"

1) create a header file eg main.h and add the following

namespace dllproj{

    extern "c" 
    {
       extern void start();
    }
    void thisstart();
}

2)add main.h to main.cpp and define thisstart()

 void dllproj::thisstart()
 {
     dllproj::start();
 }

make sure start() is declared with __declspec(dllexport) in the dll.