Writing a file is already totally unrelated
to any dialog, and unrelated to UI in general. If you had the impression that is it related in .NET, this is only because you have no clue about .NET as well, no matter how much of code you created.
Ideally, writing files should not be related to QT. Nevertheless, by some reasons (I don't think this is a place to discuss them), file support is included in QT. Please see:
With C++, you can directly use C++ API via
, but see also the comments in the QT reference page reference above, the first one.