SDK C# Read zip without downloading

Regardless of the file type, to access file data via the Dropbox API v2 .NET SDK, you can use the DownloadAsync method. That will give you a IDownloadResponse you can use to access the file data via several methods. Exactly what you do with the data is up to you. You can save it to the local filesystem, for instance, but you are not required to. You could use GetContentAsStreamAsync to get a stream of the data and pass that directly to whatever you need to do with it instead, for example.

Here's some sample code that uses the stream to update an image in place, for example, instead of saving it locally.

In your case, it sounds like you'd need to pass it to some code that can handle zip data in place. That's a bit outside the scope of Dropbox API support though, so I can't offer much guidance on that exactly, but it looks like System.IO.Compression may support unzipping zip data from a stream.