Creating modal dialog in vc++

[dhanashivam]

Hi All,

I have developed a VC+ dll file which provides a product key for my msi setup file. This VC++ dll work fine together with my setup file. but,

my problem is, i have given a message box inside the dll for showing error message while an invalid key is entered. but the messagebox is not shown as modal dialog. i must want to show this as modal dialog.

in my VC++ method i have passed the MSIHANDLE from the msi file.

how can i change the message as modal dialog?

my code is:

#include "windows.h"
#include "msi.h"
#include "msiquery.h "

extern "C" _declspec(dllex port) UINT __stdcall VerifyPID(MSIHA NDLE hInstall);

TCHAR* GetPIDValue(TCH AR*);

extern "C" UINT __stdcall VerifyPID(MSIHA NDLE hInstall)
{
UINT nRetVal = 0;
UINT uiMsiRc;
TCHAR szPidKey[MAX_PATH];
TCHAR szSourceDir[MAX_PATH];
TCHAR* lpszPidValue;
DWORD dwBuffer;

dwBuffer = sizeof(szSource Dir)/sizeof(TCHAR);

uiMsiRc = MsiGetProperty( hInstall, TEXT("SourceDir "), szSourceDir, &dwBuffer);

if (ERROR_SUCCESS != uiMsiRc)
{
MessageBox(NULL , "Not able to retrieve the SourceDir property. The setup may be corrupt. Please contact Technical Support.", "Setup Error", MB_OK | MB_ICONEXCLAMAT ION);
return 0;
}

lpszPidValue = GetPIDValue(szS ourceDir);

dwBuffer = sizeof(szPidKey )/sizeof(TCHAR);

uiMsiRc = MsiGetProperty( hInstall, TEXT("PIDKEY"), szPidKey, &dwBuffer);

if (ERROR_SUCCESS != uiMsiRc)
{
MessageBox(NULL , "Not able to retrieve PIDKEY property. The setup may be corrupt. Please contact Technical Support.", "Setup Error", MB_OK | MB_ICONEXCLAMAT ION);
return 0;
}

int str = lstrcmp(szPidKe y, lpszPidValue);

if (str == 0)
MsiSetProperty( hInstall, "PIDCHECK", "TRUE");
else
{
MsiSetProperty( hInstall, "PIDCHECK", "FALSE");
MessageBox(NULL ,"Please enter the correct product registration code!", "Invalid Key", MB_OK | MB_ICONINFORMAT ION);
}
return 0;
}

TCHAR* GetPIDValue(TCH AR* lpszSourceDir)
{
return "123-456-789";
}

Please help to resolve it.

Thanks in advance.

Regards,
Dhanasekaran. G

[weaknessforcats]

Your code works for me after I changed it this way:

void __stdcall DisplayFromDll()
{
    MessageBox(NULL, TEXT("Not able to retrieve the SourceDir property. The setup may be corrupt. Please contact Technical Support."), TEXT("Setup Error"), MB_OK | MB_ICONEXCLAMATION);
 
}
 

Notice I used the TEXT macro. Otherwise, your code won't compile.

Next, be sure your DLL project has a DEF file that exports the C++ name as a name you can use with GetProcAddress:

;BEGIN ADLL.DEF FILE
;This DEF file is required becuase the argument to GetProcAddress()
;for the function is a C-string and it will never be equal to the
;C++ mangled name for the function
;This DEF file maps the mangled name to a name that can be used with GetProcAddress()
;Note also: Change project settings in Visual Studio to send the LINK this def file.
;Visual Studio.NET: Project Properties/Linker/Input/Module Definition File/...Path to the def file\Adll.def
LIBRARY ADll 
EXPORTS 
;Exported Name    C++ Mangled Name
DisplayFromDll =  ?DisplayFromDll@@YGXXZ
;END DEF FILE 
 

Next, be certain to set the path to the DEF file in the linker input project property.

Finally, I called the funciton:

//First, load the dll into memory
    HMODULE theDll = LoadLibrary(TEXT("C:\\Scratch\\Instructor\\Debug\\DLLExample.dll"));
    if (!theDll)
    {
        MessageBox(NULL, TEXT("Dll Failed to Load"), TEXT("Fatal Error"), MB_OK | MB_ICONEXCLAMATION);
        return 1;
    }
 
    //Second, get the address of the desried function from the dll
    FARPROC addr = GetProcAddress(theDll, "DisplayFromDll");
    if (!addr)
    {
 
        //Look up the error in the system errors list
        unsigned int what = GetLastError();
        if (what == ERROR_PROC_NOT_FOUND)
        {
            MessageBox(NULL, TEXT("Function not found in the dll"), TEXT("Fatal Error"), MB_OK | MB_ICONEXCLAMATION);
 
        }
        return 2;
    }
    cout << "The function has been located in the dll" << endl;
    //Declare a function pointer that can accept the address of the function.
    //You will need to know the function prototype to do this.
    //Dll function prototypes should be provided by the vendor of the dll
    void (__stdcall *DisplayFromDll)();
    //Type-cast the address returned from GetProcAddress to the function pointer type
    DisplayFromDll = reinterpret_cast<void (__stdcall *)()>  (addr);
    //Now use the function pointer to call the function:
    DisplayFromDll();