resolve the nested if in https://msdn.microsoft.com/en-us/library/windows/desktop/bb776913(v=vs.85).aspx

BasicFileOpen.cpp

#define FAILED(x) (!SUCCEEDED(x))

HRESULT BasicFileOpen()
{
    // CoCreate the File Open Dialog object.
    IFileDialog *pfd = NULL;
    HRESULT hr = CoCreateInstance(CLSID_FileOpenDialog, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pfd));
    if (FAILED(hr)) return hr;

    // Create an event handling object, and hook it up to the dialog.
    IFileDialogEvents *pfde = NULL;
    hr = CDialogEventHandler_CreateInstance(IID_PPV_ARGS(&pfde));
    if (SUCCEEDED(hr)) {

        // Hook up the event handler.
        DWORD dwCookie;
        hr = pfd->Advise(pfde, &dwCookie);
        if (SUCCEEDED(hr)) {
            // show dialog
            hr = ShowFileDialog(hr, pfd, pfde)
            // Unhook the event handler.
            pfd->Unadvise(dwCookie);
        }
        pfde->Release();
    }
    pfd->Release();

    return hr;
}


void ShowFileDialog(HRESULT hr, IFileDialog *pfd, IFileDialogEvents *pfde) {
    // Set the options on the dialog.
    DWORD dwFlags;

    // Before setting, always get the options first in order
    // not to override existing options.
    hr = pfd->GetOptions(&dwFlags);
    if(FAILED(hr)) return hr;

    // In this case, get shell items only for file system items.
    hr = pfd->SetOptions(dwFlags | FOS_FORCEFILESYSTEM);
    if(FAILED(hr)) return hr;

    // Set the file types to display only.
    // Notice that this is a 1-based array.
    hr = pfd->SetFileTypes(ARRAYSIZE(c_rgSaveTypes), c_rgSaveTypes);
    if(FAILED(hr)) return hr;

    // Set the selected file type index to Word Docs for this example.
    hr = pfd->SetFileTypeIndex(INDEX_WORDDOC);
    if(FAILED(hr)) return hr;

    // Set the default extension to be ".doc" file.
    hr = pfd->SetDefaultExtension(L"doc;docx");
    if(FAILED(hr)) return hr;

    // Show the dialog
    hr = pfd->Show(NULL);
    if(FAILED(hr)) return hr;

    // Obtain the result once the user clicks
    // the 'Open' button.
    // The result is an IShellItem object.
    IShellItem *psiResult;
    hr = pfd->GetResult(&psiResult);
    if(FAILED(hr)) return hr;

    // We are just going to print out the
    // name of the file for sample sake.
    PWSTR pszFilePath = NULL;
    hr = psiResult->GetDisplayName(SIGDN_FILESYSPATH, &pszFilePath);
    if(FAILED(hr)) {
        psiResult->Release();
        return hr;
    }

    TaskDialog(
        NULL,
        NULL,
        L"CommonFileDialogApp",
        pszFilePath,
        NULL,
        TDCBF_OK_BUTTON,
        TD_INFORMATION_ICON,
        NULL
    );
    CoTaskMemFree(pszFilePath);

    return hr;
}