The GetFilterIndex method returns the file type contained in the DlgResults component, that the user selected in the File Save As dialog.
short sFilterIndex = spIDlgResults->GetFilterIndex();
...
// Retrieve the filename and destination directory entered by the user
IDlgResultsPtr spIDlgResults(spIFileSaveAsDlg);
std::cout << "FileName=" << (LPCSTR) spIDlgResults->GetFileName() << std::endl;
std::cout << "DirectoryName=" << (LPCSTR) spIDlgResults->GetDirectoryName() << std::endl;
std::cout << "FullPathName=" << (LPCSTR) spIDlgResults->GetFullPathName() << std::endl;
std::cout << "FilterIndex=" << spIDlgResults->GetFilterIndex() << std::endl;
std::cout << "ErrorCode=" << spIDlgResults->GetErrorCode() << std::endl;
std::cout << "ErrorMessage=" << (LPCSTR) spIDlgResults->GetErrorMessage() << std::endl;
std::cout << "Flags=" << spIDlgResults->GetFlags() << std::endl;
...