class ZipLib
{
 public static string Zip(string value)
 {
  //Transform string into byte[] 
  byte[] byteArray = new byte[value.Length];
  int indexBA = 0;
  foreach (char item in value.ToCharArray())
  {
 byteArray[indexBA++] = (byte)item;
  }
  //Prepare for compress
  System.IO.MemoryStream ms = new System.IO.MemoryStream();
  System.IO.Compression.GZipStream sw = new System.IO.Compression.GZipStream(ms,
 System.IO.Compression.CompressionMode.Compress);
  //Compress
  sw.Write(byteArray, 0, byteArray.Length);
  //Close, DO NOT FLUSH cause bytes will go missing...
  sw.Close();
  //Transform byte[] zip data to string
  byteArray = ms.ToArray();
  System.Text.StringBuilder sB = new System.Text.StringBuilder(byteArray.Length);
  foreach (byte item in byteArray)
  {
 sB.Append((char)item);
  }
  ms.Close();
  sw.Dispose();
  ms.Dispose();
  return sB.ToString();
 }
 public static string UnZip(string value)
 {
  //Transform string into byte[]
  byte[] byteArray = new byte[value.Length];
  int indexBA = 0;
  foreach (char item in value.ToCharArray())
  {
 byteArray[indexBA++] = (byte)item;
  }
  //Prepare for decompress
  System.IO.MemoryStream ms = new System.IO.MemoryStream(byteArray);
  System.IO.Compression.GZipStream sr = new System.IO.Compression.GZipStream(ms, System.IO.Compression.CompressionMode.Decompress);
  //Reset variable to collect uncompressed result
  byteArray = new byte[byteArray.Length];
  //Decompress
  int rByte = sr.Read(byteArray, 0, byteArray.Length);
  //Transform byte[] unzip data to string
  System.Text.StringBuilder sB = new System.Text.StringBuilder(rByte);
  //Read the number of bytes GZipStream red and do not a for each bytes in
  //resultByteArray;
  for (int i = 0; i < rByte; i++)
  {
 sB.Append((char)byteArray[i]);
  }
  sr.Close();
  ms.Close();
  sr.Dispose();
  ms.Dispose();
  return sB.ToString();
 }
}

string str_org="aaaaaaaaaabbbbbbbbbbbbcccccccccdddddddd";
string str_comp = ZipLib.Zip(str_org);
Console.WriteLine("str_comp:" + str_comp);
string str_uncomp = ZipLib.UnZip(str_comp);
Console.WriteLine("str_uncomp:" + str_uncomp);
Console.ReadLine();