Async Zip-on-the-Fly

Example of dynamically generating a zip file download from ASP.NET, with minimal threading and memory usage.

Specifically, with this code:

• No file is ever completely in memory at any time. As files are read, they are immediately compressed and sent to the browser.
• No threads are ever blocked waiting on reads or writes. The fully-asynchronous code permits threads to return to the thread pool unless they are actually executing code.

There are five examples in this repository, each on its own branch:

• net6-ziparchive - ASP.NET (.NET 6.0) using the built-in ZipArchive
• core-ziparchive - ASP.NET (.NET Core 1.0) using the built-in ZipArchive
• core-dotnetzip - ASP.NET (.NET Core 1.0) using DotNetZip (which restricts this application to the full .NET Framework)
• full-ziparchive - ASP.NET (.NET 4.6.1) using the built-in ZipArchive
• full-dotnetzip - ASP.NET (.NET 4.6.1) using DotNetZip

The core-ziparchive and full-ziparchive branches include a workaround for a bug in the ZipArchive class on those platforms. The net6-ziparchive does not include that workaround since the bug has been fixed.

The net6-ziparchive, core-ziparchive, and core-dotnetzip branches include their own FileCallbackResult to asynchronously stream output on demand.