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Imports System.IO  
'...
Public Shared Function Zip(text As String) As String
  Dim buffer As Byte() = System.Text.Encoding.Unicode.GetBytes(text)
  Dim ms As New MemoryStream()
  Using zipStream As New System.IO.Compression.GZipStream(ms, System.IO.Compression.CompressionMode.Compress, True)
    zipStream.Write(buffer, 0, buffer.Length)
  End Using

  ms.Position = 0
  Dim outStream As New MemoryStream()

  Dim compressed As Byte() = New Byte(ms.Length - 1) {}
  ms.Read(compressed, 0, compressed.Length)

  Dim gzBuffer As Byte() = New Byte(compressed.Length + 3) {}
  System.Buffer.BlockCopy(compressed, 0, gzBuffer, 4, compressed.Length)
  System.Buffer.BlockCopy(BitConverter.GetBytes(buffer.Length), 0, gzBuffer, 0, 4)
  Return Convert.ToBase64String(gzBuffer)
End Function

Public Shared Function UnZip(compressedText As String) As String
  Dim gzBuffer As Byte() = Convert.FromBase64String(compressedText)
  Using ms As New MemoryStream()
    Dim msgLength As Integer = BitConverter.ToInt32(gzBuffer, 0)
    ms.Write(gzBuffer, 4, gzBuffer.Length - 4)

    Dim buffer As Byte() = New Byte(msgLength - 1) {}

    ms.Position = 0
    Using zipStream As New System.IO.Compression.GZipStream(ms, System.IO.Compression.CompressionMode.Decompress)
      zipStream.Read(buffer, 0, buffer.Length)
    End Using

    Return System.Text.Encoding.Unicode.GetString(buffer, 0, buffer.Length)
  End Using
End Function