I tried using the async streams library. It brings up the wait/close dialog. Is there a way to make it not come up during long running operations? It needs to write for a long period of time. A database would not be suitable as it's a new format.
AsyncStreams never blocks the main thread. However the code that calls AStream.Write can block the main thread. It is hard to assist without seeing any of the code. You can add DoEvents to prevent the ANR dialog.