In one use case I generate a ZIP file in the temp folder and I want the API to return this ZIP file. NancyFx contains a Responses.AsFile helper but it works only with paths relative to the application.
If you have an absolute path of a file, you cannot use it. You need to create a StreamResponse and return the file as an attachment
var file = new FileStream(zipPath, FileMode.Open); string fileName = //set a filename var response = new StreamResponse(() => file, MimeTypes.GetMimeType(fileName)); return response.AsAttachment(fileName);