.net2.0文件压缩/解压缩

using System;
using System.IO;
using System.IO.Compression;

public class Zip
{
    /// <summary>
    /// 压缩
    /// </summary>
    /// <param name="sourceFile">源文件名,如a.txt</param>
    /// <param name="destinationFile">目标文件名,如a.rar</param>
      public static void CompressFile(string sourceFile, string destinationFile)
      {
        if (!File.Exists(sourceFile)) throw new FileNotFoundException();
      using (FileStream sourceStream = new FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read))
      {
        byte [] buffer = new byte[sourceStream.Length];
        int checkCounter = sourceStream.Read(buffer, 0, buffer.Length);
        if (checkCounter != buffer.Length) throw new ApplicationException();
          using (FileStream destinationStream = new FileStream(destinationFile, FileMode.OpenOrCreate, FileAccess.Write))
          {
            using (GZipStream compressedStream = new GZipStream(destinationStream, CompressionMode.Compress, true))
            {
              compressedStream.Write(buffer, 0, buffer.Length);
            }
          }
        }
      }
   
    /// <summary>
    /// 解压缩
    /// </summary>
    /// <param name="sourceFile">源文件名,如a.rar</param>
    /// <param name="destinationFile">目标文件名,如a.txt</param>
    public static void DecompressFile(string sourceFile, string destinationFile)
      {
        if (!File.Exists( sourceFile)) throw new FileNotFoundException();
      using (FileStream sourceStream = new FileStream(sourceFile, FileMode.Open))
        {
        byte [] quartetBuffer = new byte[4];
        int position = (int)sourceStream.Length - 4;
        sourceStream.Position = position;
        sourceStream.Read(quartetBuffer, 0, 4);
        sourceStream.Position = 0;
        int checkLength = BitConverter.ToInt32(quartetBuffer, 0);
        byte[] buffer = new byte[checkLength + 100];
          using (GZipStream decompressedStream = new GZipStream(sourceStream, CompressionMode.Decompress, true))
          {
            int total = 0;
          for (int offset = 0; ; )
          {
            int bytesRead = decompressedStream.Read(buffer, offset, 100);
            if (bytesRead == 0) break;
            offset += bytesRead;
            total += bytesRead;
          }
              using (FileStream destinationStream = new FileStream(destinationFile, FileMode.Create))
              {
                destinationStream.Write(buffer, 0, total);
                destinationStream.Flush();
              }
        }
      }
    }
}