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Posted 2 May 2004


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How to load a dynamic link library (DLL) into a Microsoft Visual C++ 6.0 project

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6 May 20042 min read
This article gives guidelines for loading a DLL into your project and accessing the services offered by the DLL.


In this article, I will summarize the results of my investigation with respect to including a dynamic link library (DLL) into a Microsoft Visual C++ 6.0 project, and using services which are offered by the loaded DLL.

The purpose of this article is to explain in short, but explicitly, what you need to do in order to be able to use services included in a DLL (by services, I refer to any function, a class or a parameter exported into DLL). Three weeks of “DLL hell” I went through can be avoided by doing the steps described below.

Case 1: A DLL you are supplied with is provided by another application and has been generated with the help of OLE (COMM).

Example: I needed to access an external interface of Rose-RT, which has been provided by the developers of Rose-RT as RrtRes.dll in order to control Rose-RT from external application.

Steps to perform:

  • Create in Microsoft Visual C++ 6.0 an MFC application (.dll or .exe);
  • Go to the menu View, ClassWizard.
  • Select an option Add Class…, from a type library.
  • Browse to the location of your *.dll.
  • A window, which displays the content of your *.dll, will appear. Select all classes you want to include in your project (Ctrl+A – select all content, or Ctrl + mouse click – for selecting a specific set of classes).
  • Push the button Open. Header file *.h and *.cpp implementation file will be generated.
  • Close the ClassWizard.

Now, all services you selected for use in you project are available!

Case 2: A DLL you are supplied with has been generated as a MFC-shared DLL and it is to be used in a single-threaded code

Example: Suppose you are supplied with LoadMe.dll, services of which should be accessed, but which cannot be exported as mentioned in case 1.

//You need to declare types to point on classes/functions in LoadMe.dll
//Assume, you have a function in your LoadMe.dll with a name 
//EntryPoint, which takes two parameters of types int and const char *, 
//and is of type void. You need to create a new type as a 
//pointer to that function as it is shown below.

typedef void (*EntryPointfuncPtr)(int argc, const char * argv );  
//Declare an HINSTANCE and load the library dynamically. Don’t forget 
//to specify a correct path to the location of LoadMe.dll

LoadMe = LoadLibrary("..\\enter a Path To Your Dll here\\LoadMe.dll");
// Check to see if the library was loaded successfully 
if (LoadMe != 0)
    printf("LoadMe library loaded!\n");
    printf("LoadMe library failed to load!\n");

//declare a variable of type pointer to EntryPoint function, a name of 
// which you will later use instead of EntryPoint
EntryPointfuncPtr LibMainEntryPoint;            

// GetProcAddress – is a function, which returns the address of the 
// specified exported dynamic-link library (DLL) function. After 
// performing this step you are allowed to use a variable 
// LibMainEntryPoint as an equivalent of the function exported in 
// LoadMe.dll. In other words, if you need to call 
// EntryPoint(int, const char *) function, you call it as 
// LibMainEntryPoint(int, const char *)

LibMainEntryPoint = (EntryPointfuncPtr)GetProcAddress(LoadMe,"entryPoint");

Now, you can access any of the services of LoadMe.dll. Good luck!

Case 3: A DLL you are supplied with has been generated as a MFC-shared DLL and it is to be used in a multithreaded code

Use AfxLoadLibrary() instead of LoadLibrary() mentioned in case 2.

When you are done, don't forget to free the memory and unload the library: FreeLibrary(LoadMe).


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Nataliya Mulyar
Web Developer
Netherlands Netherlands
I have BSc and MSc in Automatics and Computer Control Systems. After graduation I followed a post-master program Software Technology. Until the end of august 2004 I was involved in 9-month graduation project at the Embedded Systems Institute (Netherlands), where I was busy with coupling of Matlab/Simulink and Rational Rose RealTime. From September I switched to a new domain, so now I work on the development of patterns for process-aware information systems. My hobbies are painting, chess and dynamic sport.

Comments and Discussions

GeneralMy vote of 4 Pin
Oshtri Deka7-Apr-11 22:30
professionalOshtri Deka7-Apr-11 22:30 
QuestionGetProcAddress Fail in VC++ App while using VB Dll Pin
JothiMurugeswaran12-Nov-07 20:29
MemberJothiMurugeswaran12-Nov-07 20:29 
QuestionNot Working Pin
JothiMurugeswaran12-Nov-07 18:45
MemberJothiMurugeswaran12-Nov-07 18:45 
GeneralThanks Pin
nickdoe20-Oct-07 14:43
Membernickdoe20-Oct-07 14:43 
QuestionHow to use VB6 DLL in VC++ Pin
Amit Joshi CP11-Jul-07 3:21
MemberAmit Joshi CP11-Jul-07 3:21 
AnswerRe: How to use VB6 DLL in VC++ Pin
Nataliya Mulyar11-Jul-07 3:42
MemberNataliya Mulyar11-Jul-07 3:42 
QuestionRe: How to use VB6 DLL in VC++ [modified] Pin
Amit Joshi CP11-Jul-07 20:39
MemberAmit Joshi CP11-Jul-07 20:39 
Hi Nataliya thanks for reply.

Very first thing I would like to clear is I am very new to C++. I am working with C++ first time for last 2 weeks.

I have one dll in Visual Basic 6 that downloads url using HTTP protocol to the system cache. This dll is working very fine. No any error.
Only problem is, till dll is downloading file, application is locked. The function I am using to download url is blocking function.

I read one article on code project which was showing how to download url asynchronously so that it will not block the user interface. But that article is in C++. He have acomplished it by creating new thread in C++.

As I told you before, I am new bye to C++. I have never used C++ before. For that reason, I am unable to understood where to write the code you specified in Case 2.

My target is to import function from Visual Basic dll into C++. Write one function in C++ that will call VB function in different thread. Export C++ function outside the dll so that I can call it form Visual Basic EXE project or ASP project whatever.

So, would you PLEASE explain me what should I do step by step ?
My e_mail id is
Thanks in advance. Waiting for your reply.


-- modified at 2:52 Thursday 12th July, 2007
GeneralRe: How to use VB6 DLL in VC++ Pin
JothiMurugeswaran12-Nov-07 18:52
MemberJothiMurugeswaran12-Nov-07 18:52 
Generalspirit of freshness Pin
i_a_z9-Aug-06 1:01
Memberi_a_z9-Aug-06 1:01 
Generaltaliya,difference between loadlibrary and afxloadlibrary Pin
psyclope13-Jun-06 19:15
Memberpsyclope13-Jun-06 19:15 
Generaltaliya,difference between loadlibrary and afxloadlibrary Pin
psyclope13-Jun-06 19:13
Memberpsyclope13-Jun-06 19:13 
Generalhi nataliya mulyar iam new to DLL...please help me... Pin
thukaram.vh1-Apr-06 1:42
Memberthukaram.vh1-Apr-06 1:42 
GeneralRe: hi nataliya mulyar iam new to DLL...please help me... Pin
Nataliya Mulyar2-Apr-06 23:46
MemberNataliya Mulyar2-Apr-06 23:46 
Generalmemory issue Pin
rahulbkarn6-Jan-06 0:40
Memberrahulbkarn6-Jan-06 0:40 
GeneralLoading dll's as Rose Real Time Add-in Pin
Daniel Lélis Baggio21-Dec-05 7:00
MemberDaniel Lélis Baggio21-Dec-05 7:00 
GeneralBest Wishes ! Pin
progman10-Nov-05 10:23
Memberprogman10-Nov-05 10:23 
GeneralGlobal variable is always NULL in my dlls Pin
Duke_Matheffy19-Jul-05 20:38
MemberDuke_Matheffy19-Jul-05 20:38 
GeneralRe: Global variable is always NULL in my dlls Pin
Anonymous19-Jul-05 23:43
MemberAnonymous19-Jul-05 23:43 
GeneralRe: Global variable is always NULL in my dlls Pin
Duke_Matheffy19-Jul-05 23:57
MemberDuke_Matheffy19-Jul-05 23:57 
GeneralRe: Global variable is always NULL in my dlls Pin
Anonymous3-Aug-05 21:22
MemberAnonymous3-Aug-05 21:22 
GeneralRe: Global variable is always NULL in my dlls Pin
Duke_Matheffy4-Aug-05 0:53
MemberDuke_Matheffy4-Aug-05 0:53 
GeneralRe: Global variable is always NULL in my dlls Pin
ima_c++_programmer21-May-07 22:50
Memberima_c++_programmer21-May-07 22:50 
GeneralTapping on cards.dll Pin
mbolanosd19-Jul-05 0:16
Membermbolanosd19-Jul-05 0:16 
GeneralRe: Tapping on cards.dll Pin
Anonymous19-Jul-05 23:32
MemberAnonymous19-Jul-05 23:32 
Generalexternal interface of Rose-RT Pin
mehdi_ab18-Jul-05 4:32
Membermehdi_ab18-Jul-05 4:32 

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