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Introduction

This article shows a step-by-step technique to create your first DLL with VC++.

Steps to Create Your First DLL

• Create a Win32 Dynamic Link Library project, adding a *.cpp and a *.h file.
• In the *.cpp file, create a class instantiated from the CWinApp file.

  # include <stdafx.h>
  # include "SourceFile.h"
  
  class CDllApp : public CWinApp
  {
      public:
    
          CDllApp::CDllApp()
          {
              Calc(0,0);
          }
  
          DECLARE_MESSAGE_MAP()
  };
  
  BEGIN_MESSAGE_MAP(CDllApp,CWinApp)
  
  END_MESSAGE_MAP()
  
  CDllApp DllObject;

• In the *.h file (here it is SourceFile.h), define the functions to be used. Also specify the dllexport value for the _declspec function.

  extern "C" _declspec(dllexport) int Calc(char no1,char no2)
  {
      char result;
      result = no1 + no2;
      return result;
  }

• Then compile the DLL.
• Create a normal Win32 Application with a *.cpp file and a *.h file.
• In the *.h file, (here it is AppHeader.h ), declare the function with the dllimport value of _declspec.

   extern "C" _declspec(dllimport) Calc(int FirstValue,
       int SecondValue);

• In the *.cpp file, use the function.

  # include "AFXWIN.H"
  # include "AppHeader.h"
  
  class MainFrame : public CFrameWnd
  {
      public:
  
          MainFrame()
          {
              Create(0,"Trial");
          }
  
          void OnLButtonDown(UINT nFlags,CPoint point)
          {
              int res;
              char str[5];
              res = Calc(998,226);
              sprintf(str,"%d",res);
              MessageBox(str);
           }
  
           DECLARE_MESSAGE_MAP()
  };

• In the Link tab of the "Project->Settings" dialog, go to the text box labeled "Object / Library Modules" and specify the path of the DLL file. Then copy the compiled DLL file to your current appliation path directory and run the program.

Some Things to Note

The DLL file may not be visible due to the File View options in the Windows folder. So, you can either go to the DOS prompt and copy the file or enable the setting "Show all files" in Windows Explorer to copy the file. To create a DLL that uses MFC, see the following example. Note that extern "C" has not been used and the macro AFX_MANAGE_STATE(AfxGetStaticModuleState()); has been used to implement MFC.

 _declspec(dllexport)CString Display(CString a,CString b)
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());
    CString Str;
    Str = a + b;
    return Str;
}

That's all, folks. All luck and have a great time.

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How can i create a same type of dll in vb6? JothiMurugeswaran 19:19 13 Nov '07   Do you have any idea on creating this dll from vb6 ( With Export Functions ) Jothi Murugeswaran.S Sign In·View Thread·PermaLink 1.00/5 building dll (C++) to be called by C applications P.Luke 14:33 20 Apr '07   Hi I am new to dll file. I get stuck with building a dll (C/C++) file to be call from C applications in VS.NET 2003 for my project. Does anyone know how to properly build and import it , something like extern "C" __declspec( dllexport ) int MyFunc(long parm1);. I try to do it but it just didn't work. Practical examples would be really good!! many thanks Sign In·View Thread·PermaLink 2.00/5 Dll-ASP.NET 1:10 23 Feb '07   how to create dll file in asp.net Gayatri Sign In·View Thread·PermaLink 1.50/5 Messages Gipico 4:32 27 Oct '06   Hi, How do I send messages from my DLL to the app loading the DLL? Thanks for an informative article Cheers Sign In·View Thread·PermaLink C DLL without changing the source code saflitzk 11:47 8 Mar '05   1)How can i creat a .dll file from c code (no classes) without changing the source code (the functions)? 2)likewise how to use it at the project without changing it to? (except for some(not dependant at the number of the functions) lines at the headers files) Sign In·View Thread·PermaLink 2.20/5 problem with dll dnqhung 2:24 10 Jun '04   I have some problem with inpout32.dll in win32 console application project my code is: #include "stdio.h" #include "string.h" #include "stdlib.h" /* ----Prototypes of Inp and Outp--- */ void _stdcall Out32(short PortAddress, short data); /*--------------------------------*/ /* int main() { Out32(888,20); return 0; } but in MFC project ,it error (i use the same code ,except int out() { Out32(888,20); return 0; } Linking... thulpt1Dlg.obj : error LNK2001: unresolved external symbol "void __stdcall Out32(short,short)" (?Out32@@YGXFF@Z) Debug/thulpt1.exe : fatal error LNK1120: 1 unresolved externals Error executing link.exe. thulpt1.exe - 2 error(s), 0 warning(s) how can i solve it ? please help me dnqhung Sign In·View Thread·PermaLink 1.00/5 Re: problem with dll Christian Kluin 12:31 14 Jun '04   Well, i didnt tried this example, but i think the problem lies in different definitions of the dll-call. First it is declared as ... int Calc(char no1,char no2) --------^-------^ ... In the application is something expected as ... Calc(int FirstValue,int SecondValue); -----^------------^ ... So the problem may or may not be in different type definitions? The compiler is looking for int/short and will only find char... Hope i could help u. C. Kluin Computer Science Student of the University of Bremen. -= Everyday is monday..I hate mondays =- Sign In·View Thread·PermaLink Error C1083 in VC++ .NET 2002 Scott H. Chang 8:07 8 Mar '04   Hi all, I used 'Empty Project'/native C++ of the VC++ .NET 2002 to do 'Build' for the .cpp and .h files of the Creation of a simple DLL project and I got an Error C1083 - can not find or open . Is already built in the VC++ .NET system? What is wrong in this 'Build'? Can someone help and point out what is wrong with this 'Build' and how to correct it? Thanks in advance, Scott Chang Sign In·View Thread·PermaLink 2.00/5 Re: Error C1083 in VC++ .NET 2002 Sachin R Sangoi 3:06 11 Jan '07   Hi jst check out if u have included the correct path for the library and directory in the options. else set the correct path in the IDE. can u write complete error string. happy coding Get the facts or facts will get you and when you get them, get them right or they will get you wrong. Happy Coding Sign In·View Thread·PermaLink how to export vb function through c++ dll sailu 21:45 22 Aug '02   hi friends, how to invoke vb dll through c++ dll. thanks in advance. Sign In·View Thread·PermaLink 1.33/5 dll compilation error MINAKANNAN 21:30 22 Jul '02   d:\mi\mi.cpp(1) : fatal error C1083: Cannot open include file: 'stdafx.h': No such file or directory Sign In·View Thread·PermaLink 1.50/5 Re: dll compilation error Anonymous 11:05 11 Mar '03   At start, then you choos type of the project select MFC AppWizard Sign In·View Thread·PermaLink 2.00/5 Re: dll compilation error Anonymous 1:43 25 Aug '04   but if i select Win32 Dynamic-Link Library i got the fatal error. i want Win32 Dynamic-Link Library, how can i remove this erro with out usaing MFC AppWizard dll. Sign In·View Thread·PermaLink Re: dll compilation error sivo 21:09 6 Apr '03   i use win32 also ; hey man ,u describe it is simple but i'm stuck in this FATAL Error: error 1083,or 2019 ,mentioning that your symbole cannot be resolved , couldn't open or read this dll and that lib , ouch please shed me a light in this issue , really i have not much time to making dll and testing resultless! Sign In·View Thread·PermaLink 1.50/5 Re: dll compilation error DaFrawg 3:08 30 Jan '04   Add the following to the declaration of each exported function (and constructor & destructor functions of any class that are accessable for other modules): __declspec(dllimport) So, if you have the function 'foo' (void foo(void)): __declspec(dllimport) void foo (); BTW, that was in the tutorial. Sign In·View Thread·PermaLink 2.00/5 Re: dll compilation error sivo 21:09 6 Apr '03   i use win32 also ; hey man ,u describe it is simple but i'm stuck in this FATAL Error: error 1083,or 2019 ,mentioning that your symbole cannot be resolved , couldn't open or read this dll and that lib , ouch please shed me a light in this issue , really i have not much time to making dll and testing resultless! Sign In·View Thread·PermaLink 2.00/5

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