Conditionally write to a compressed stream

Question

My Import method takes some data and writes it to a stream. If the CompressedStore property is true, the contents of that stream should be compressed.

This code works, however I just don't like it. For one, I call serializer.Serialize() twice. I feel this code can be made more concise. Any ideas?

public void Import(IProvisionSource source)
{
   InitializeStore();

   // Call source.Export and populate local data store
   var data = source.Export();
   var serializer = new XmlSerializer(data.GetType());

   var file = CompressedStore ? "KPCData.gz" : "KPCData.xml";
   var path = Path.Combine(DataDirectory, file);
   using (var fileWriter = new FileStream(path, FileMode.Create))
   {
      if (CompressedStore)
      {
         using (var writer = new GZipStream(fileWriter, CompressionLevel.Optimal))
         {
            serializer.Serialize(writer, data);
         }
      }
      else
      {
         serializer.Serialize(fileWriter, data);
      }
   }
}

Answer 1

By default, GZipStream owns the underlying stream, so it disposes it when it's disposed itself. If you're okay with relying on that, then you could put the right Stream into a variable and then have just one using around it. Something like:

var writer = new FileStream(path, FileMode.Create);

if (CompressedStore)
    writer = new GZipStream(writer, CompressionLevel.Optimal);

using (writer)
{
   serializer.Serialize(writer, data);
}

This avoids the duplication and so it's shorter, but it's also less obviously correct (using combined with new is a good pattern, and it's not used here), so I think your original code is actually the better option. If there was more repetition than just one method call, it could make sense to extract that into a separate method, but that's not the case here.