//Following Code will help u to decompress using ICSharpCode.SharpZipLib.GZip; Stream s = new GZipInputStream(File.OpenRead(@"C:\Sample.txt.gz")); FileStream fs = File.Create(@"C:\Sample.txt"); int size = 2048; byte[] writeData = new byte[2048]; while (true) { size = s.Read(writeData, 0, size); if (size > 0) { fs.Write(writeData, 0, size); } else { break; } } s.Close(); fs.Close(); ///Following code will use to compress the file to.gz Stream s = new GZipOutputStream(File.Create(@"C:\Sample.txt.gz")); FileStream fs = File.OpenRead(@"C:\Sample.txt"); byte[] writeData = new byte[fs.Length]; fs.Read(writeData, 0, (int)fs.Length); s.Write(writeData, 0, writeData.Length); s.Close(); fs.Close(); //Download the dll from here http://www.icsharpcode.net/OpenSource/SharpZipLib/Default.aspx