How can I have the directory read-only and its subdirectories as read-write?

You need to set the following rules (C++ syntax below):

1. CBFSFilter::AddFilterAccessRule(<span class="string">"C:\\ReadOnly\\*.*"</span>,CBFSFilter::<span class="keyword">ReadOnly</span>);

2. CBFSFilter::AddFilterAccessRule(<span class="string">"C:\\ReadOnly\\AllAccess\\*.*"</span>,(CBFSFilter::CbFltAccessFlags)<span class="number">0</span>);