Question

I want to compress a file before saving physically on the disk.

I tried using compress and decompress methods (MSDN sample code) but all methods require a file which is already physically stored on the disk.

Answer 1

The easiest way is to open the file as a Stream and wrap it with a compression API like GZipStream.

using (var fileStream = File.Open(theFilePath, FileMode.OpenOrCreate) {
  using (var stream = new GZipStream(fileStream, CompressionMode.Compress)) {
    // Write to the `stream` here and the result will be compressed
  }
}