How to unzip a file in .net

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
using System.IO.Compression;
using System.Runtime.Serialization.Formatters;
using System.Runtime.Serialization.Formatters.Binary;
using System.Xml.Serialization;
using System.Xml;
using System.Text;


namespace My.Common
{
    public class function
    {
        public static MemoryStream CompressionStream(MemoryStream ms)
        {
            MemoryStream outStream = new MemoryStream();
            using (GZipStream output = new GZipStream(outStream, CompressionMode.Compress, true))
            {
                byte[] bytes = new byte[ms.Length];
                int n;
                while ((n = ms.Read(bytes, 0, bytes.Length)) != 0)
                {
                    output.Write(bytes, 0, n);
                }
            }
            outStream.Seek(0, SeekOrigin.Begin);
            return outStream;
        }
        public static MemoryStream DeCompressionStream(MemoryStream ms)
        {
            MemoryStream outStream = new MemoryStream();
            using (GZipStream input = new GZipStream(ms, CompressionMode.Decompress, true))
            {
                byte[] bytes = new byte[4096];
                int n;
                while ((n = input.Read(bytes, 0, bytes.Length)) != 0)
                {
                    outStream.Write(bytes, 0, n);
                }
            }
            outStream.Flush();
            outStream.Seek(0, SeekOrigin.Begin);
            return outStream;
        }
        public static Stream DeCompressionStream(Stream ms)
        {
            MemoryStream outStream = new MemoryStream();
            using (GZipStream input = new GZipStream(ms, CompressionMode.Decompress, true))
            {
                byte[] bytes = new byte[4096];
                int n;
                while ((n = input.Read(bytes, 0, bytes.Length)) != 0)
                {
                    outStream.Write(bytes, 0, n);
                }
            }
            outStream.Flush();
            outStream.Seek(0, SeekOrigin.Begin);
            return (Stream)outStream;
        } 

    }
}