Question

I have a big object in memory which I want to save as a blob into database.
I want to compress it before saving because database server is usually not local.

This is what I have at the moment:

using (var memoryStream = new MemoryStream())
{
  using (var gZipStream = new GZipStream(memoryStream, CompressionMode.Compress))
  {
    BinaryFormatter binaryFormatter = new BinaryFormatter();
    binaryFormatter.Serialize(gZipStream, obj);

    return memoryStream.ToArray();
  }
}

However when I zip same bytes with Total Commander it cuts down the size always by 50% at least. With the above code it compresses 58MB to 48MB and anything smaller than 15MB gets even bigger.

Should I use a third-party zip library or is there a better way of doing this in .NET 3.5.
Any other alternatives to my problem?

EDIT:

Just found a bug in a code above. Angelo thanks for your fix.

GZipStream compression is still not great.
I gets Average 35% compression by gZipStream compared to TC 48% compression.

I have no idea what kind of bytes I was getting out with previous version 🙂

EDIT2:

I have found how to improve compression from 20% to 47%.
I had to use two Memory streams instead of one! Can anyone explain why is this the case?

Here is a code with 2 memory streams which does a lot better compression !!!

using (MemoryStream msCompressed = new MemoryStream())
using (GZipStream gZipStream = new GZipStream(msCompressed, CompressionMode.Compress))
using (MemoryStream msDecompressed = new MemoryStream())
{
  new BinaryFormatter().Serialize(msDecompressed, obj);
  byte[] byteArray = msDecompressed.ToArray();

  gZipStream.Write(byteArray, 0, byteArray.Length);
  gZipStream.Close();
  return msCompressed.ToArray();
}

Answer 1

GZipStream from .NET 3.5 doesn’t allow you to set compression level. This parameter was introduced in .NET 4.5, but I don’t know if it will give you better result or upgrade is suitable for you.
Built in algorithm is not very optimal, due to patents AFAIK.
So in 3.5 is only one way to get better compression is to use third party library like SDK provided by 7zip or SharpZipLib. Probably you should experiment a little bit with different libs to get better compression of your data.