How to use resource for Windows API custom dialog template?

Question

I am trying to use a custom template on an OPENFILENAME struct in C++, and cannot figure out what exactly I am doing wrong. Here is what I have so far:

#include <windows.h>
#include <iostream>
#include "resource.h"

void main() {
    HWND hwnd = NULL;// owner window

    OPENFILENAME ofn;
    CHAR File[256];
    ZeroMemory(&ofn, sizeof(OPENFILENAME));

    ofn.lStructSize = sizeof(OPENFILENAME);
    ofn.hwndOwner = hwnd;
    ofn.hInstance = NULL; 
    ofn.lpstrCustomFilter = NULL;
    ofn.nMaxCustFilter = 0;
    ofn.nFilterIndex = 0;
    ofn.lpstrFile = File;
    ofn.lpstrFile[0] = '\0';
    ofn.nMaxFile = sizeof(File);
    ofn.lpstrFileTitle = NULL;
    ofn.nMaxFileTitle = MAX_PATH;
    ofn.lpstrInitialDir = NULL;
    ofn.lpstrTitle = NULL;
    ofn.Flags = OFN_ENABLETEMPLATE;
    ofn.nFileOffset = 0;
    ofn.nFileExtension = 0;
    ofn.lpstrDefExt = NULL;
    ofn.lCustData = 0L;
    ofn.lpfnHook = NULL;
    ofn.lpTemplateName = "IDD_DIALOGBAR";


    if (GetOpenFileName(&ofn)==TRUE) 
    {
        //do something with filename
    }

    std::cout << CommDlgExtendedError();
}

IDD_DIALOGBAR is a custom resource I added to the project. I did this by creating a new, empty C++ project in Visual Studio, then right clicking on the project name in the Solution Explorer, and then clicking "Add"-->"Resource". I then selected "IDD_DIALOGBAR" from the available list of resources. This added a new resource to the project, which can be viewed when I switch to "Resource View" in Visual Studio.

When I run the program, the dialog box does not appear at all. The result of CommDlgExtendedError() is CDERR_FINDRESFAILURE: The common dialog box function failed to find a specified resource.

I have also tried changing

ofn.lpTemplateName = "IDD_DIALOGBAR"

to

ofn.lpTemplateName = MAKEINTRESOURCE(IDD_DIALOGBAR)

but that resulted in a different error message:

CDERR_DIALOGFAILURE: The dialog box could not be created. The common dialog box function's call to the DialogBox function failed. For example, this error occurs if the common dialog box call specifies an invalid window handle.

What am I missing? Am I not referencing the resource correctly?

Answer 1

ofn.hInstance needs to be set to the HINSTANCE of the module (executable or DLL) that has the dialog template resource.