C#におけるtar.gz ref: http://qiita.com/ntk1000@github/items/edbd7e85bde8f5cd2c9b

file0.cs

using ICSharpCode.SharpZipLib.GZip;
using ICSharpCode.SharpZipLib.Tar;

public void CreateGz(string outputFilePath, string inputFilePath)
{
    using (FileStream infs = new FileStream(inputFilePath, FileMode.Open, FileAccess.Read))
    using (FileStream outfs = new FileStream(outputFilePath, FileMode.Create, FileAccess.Write, FileShare.None))
    using (GZipOutputStream gzipStream = new GZipOutputStream(outfs))
    {
        gzipStream.SetLevel(1);// 圧縮レベル: デフォルト6で遅いので強制的に1にセット
        try
        {
            infs.CopyTo(gzipStream);
        }
        catch
        {
            throw;// 例外処理
        }
    }
}

file1.cs

using ICSharpCode.SharpZipLib.GZip;
using ICSharpCode.SharpZipLib.Tar;

public void CreateTarGz(string outputTarFilePath, string sourceDirectory)
{
    using (FileStream fs = new FileStream(outputTarFilePath, FileMode.Create, FileAccess.Write, FileShare.None))
    using (GZipOutputStream gzipStream = new GZipOutputStream(fs))
    {
        gzipStream.SetLevel(1);
        using (TarArchive tarArchive = TarArchive.CreateOutputTarArchive(gzipStream))
        {
            try
            {
                Directory.EnumerateFiles(sourceDirectory)
                    .ToList()
                    .ForEach(x =>
                    {
                        var tarEntry = TarEntry.CreateEntryFromFile(x);
                        tarEntry.Name = Path.GetFileName(x);
                        tarArchive.WriteEntry(tarEntry, false);
                    });
            }
            catch
            {
                throw;
            }
        }
    }
}