public ZipEntry AddEntry(string entryName, WriteDelegate writer)
{
 ZipEntry ze = ZipEntry.CreateForWriter(entryName, writer);
 if (this.Verbose)
 {
  this.StatusMessageTextWriter.WriteLine("adding {0}...", entryName);
 }
 return this._InternalAddEntry(ze);
}

public void Save()
{
 try
 {
  bool flag = false;
  this._saveOperationCanceled = false;
  this._numberOfSegmentsForMostRecentSave = 0;
  this.OnSaveStarted();
  if (this.WriteStream == null)
  {
   throw new BadStateException("You haven't specified where to save the zip.");
  }
  if (((this._name != null) && this._name.EndsWith(".exe")) && !this._SavingSfx)
  {
   throw new BadStateException("You specified an EXE for a plain zip file.");
  }
  if (!this._contentsChanged)
  {
   this.OnSaveCompleted();
   if (this.Verbose)
   {
    this.StatusMessageTextWriter.WriteLine("No save is necessary....");
   }
  }
  else
  {
   this.Reset(true);
   if (this.Verbose)
   {
    this.StatusMessageTextWriter.WriteLine("saving....");
   }
   if ((this._entries.Count >= 0xffff) && (this._zip64 == Zip64Option.Default))
   {
    throw new ZipException("The number of entries is 65535 or greater. Consider setting the UseZip64WhenSaving property on the ZipFile instance.");
   }
   int current = 0;
   ICollection<ZipEntry> entries = this.SortEntriesBeforeSaving "." + Path.GetRandomFileName();
      if (File.Exists(path))
      {
       this.DeleteFileWithRetry(path);
      }
      File.Move(this._name, path);
     }
     this.OnSaveEvent(ZipProgressEventType.Saving_BeforeRenameTempArchive);
     File.Move((writeStream != null) "htmlcode">

public static bool IsZipFile(Stream stream, bool testExtract)
{
 if (stream == null)
 {
  throw new ArgumentNullException("stream");
 }
 bool flag = false;
 try
 {
  if (!stream.CanRead)
  {
   return false;
  }
  Stream @null = Stream.Null;
  using (ZipFile file = Read(stream, null, null, null))
  {
   if (testExtract)
   {
    foreach (ZipEntry entry in file)
    {
     if (!entry.IsDirectory)
     {
      entry.Extract(@null);
     }
    }
   }
  }
  flag = true;
 }
 catch (IOException)
 {
 }
 catch (ZipException)
 {
 }
 return flag;
}



2.Read()读取数据流：




 private static ZipFile Read(Stream zipStream, TextWriter statusMessageWriter, Encoding encoding, EventHandler<ReadProgressEventArgs> readProgress)
{
 if (zipStream == null)
 {
  throw new ArgumentNullException("zipStream");
 }
 ZipFile zf = new ZipFile {
  _StatusMessageTextWriter = statusMessageWriter,
  _alternateEncoding = encoding "reading from stream...");
 }
 ReadIntoInstance(zf);
 return zf;
}



以上是对ZipFile类的一些方法的解析，提供了该组件的一些方法的源码，至于源码的解读上难度不是很大，至于该组件的API，可以在下载DLL文件后，可以直接查看相应的方法和属性，在这里就不做详细的介绍。
三.DotNetZip组件使用实例：
以上是对该组件的一些解析，接下来我们看看实例：
1.压缩ZIP文件：




/// <summary>
  /// 压缩ZIP文件
  /// 支持多文件和多目录，或是多文件和多目录一起压缩
  /// </summary>
  /// <param name="list">待压缩的文件或目录集合</param>
  /// <param name="strZipName">压缩后的文件名</param>
  /// <param name="isDirStruct">是否按目录结构压缩</param>
  /// <returns>成功：true/失败：false</returns>
  public static bool CompressMulti(List<string> list, string strZipName, bool isDirStruct)
  {
   if (list == null)
   {
    throw new ArgumentNullException("list");
   }
   if (string.IsNullOrEmpty(strZipName))
   {
    throw new ArgumentNullException(strZipName);
   }
   try
   {
    //设置编码，解决压缩文件时中文乱码
    using (var zip = new ZipFile(Encoding.Default))
    {
     foreach (var path in list)
     {
      //取目录名称
      var fileName = Path.GetFileName(path);
      //如果是目录
      if (Directory.Exists(path))
      {
       //按目录结构压缩
       if (isDirStruct)
       {
        zip.AddDirectory(path, fileName);
       }
       else
       {
        //目录下的文件都压缩到Zip的根目录
        zip.AddDirectory(path);
       }
      }
      if (File.Exists(path))
      {
       zip.AddFile(path);
      }
     }
     //压缩
     zip.Save(strZipName);
     return true;
    }
   }
   catch (Exception ex)
   {
    throw new Exception(ex.Message);
   }
  }



2.解压ZIP文件：




/// <summary>
  /// 解压ZIP文件
  /// </summary>
  /// <param name="strZipPath">待解压的ZIP文件</param>
  /// <param name="strUnZipPath">解压的目录</param>
  /// <param name="overWrite">是否覆盖</param>
  /// <returns>成功：true/失败：false</returns>
  public static bool Decompression(string strZipPath, string strUnZipPath, bool overWrite)
  {
   if (string.IsNullOrEmpty(strZipPath))
   {
    throw new ArgumentNullException(strZipPath);
   }
   if (string.IsNullOrEmpty(strUnZipPath))
   {
    throw new ArgumentNullException(strUnZipPath);
   }
   try
   {
    var options = new ReadOptions
    {
     Encoding = Encoding.Default
    };
    //设置编码，解决解压文件时中文乱码
    using (var zip = ZipFile.Read(strZipPath, options))
    {
     foreach (var entry in zip)
     {
      if (string.IsNullOrEmpty(strUnZipPath))
      {
       strUnZipPath = strZipPath.Split('.').First();
      }
      entry.Extract(strUnZipPath,overWrite
        "htmlcode">

/// <summary>
  /// 得到指定的输入流的ZIP压缩流对象
  /// </summary>
  /// <param name="sourceStream">源数据流</param>
  /// <param name="entryName">实体名称</param>
  /// <returns></returns>
  public static Stream ZipCompress(Stream sourceStream, string entryName = "zip")
  {
   if (sourceStream == null)
   {
    throw new ArgumentNullException("sourceStream");
   }
   var compressedStream = new MemoryStream();  
   long sourceOldPosition = 0;
   try
   {
    sourceOldPosition = sourceStream.Position;
    sourceStream.Position = 0;
    using (var zip = new ZipFile())
    {
     zip.AddEntry(entryName, sourceStream);
     zip.Save(compressedStream);
     compressedStream.Position = 0;
    }
   }
   catch (Exception ex)
   {
    throw new Exception(ex.Message);
   }
   finally
   {
    try
    {
     sourceStream.Position = sourceOldPosition;
    }
    catch (Exception ex)
    {
     throw new Exception(ex.Message);
    }
   }
   return compressedStream;
  }



4.得到指定的字节数组的ZIP解压流对象：




/// <summary>
  /// 得到指定的字节数组的ZIP解压流对象
  /// 当前方法仅适用于只有一个压缩文件的压缩包，即方法内只取压缩包中的第一个压缩文件
  /// </summary>
  /// <param name="data"></param>
  /// <returns></returns>
  public static Stream ZipDecompress(byte[] data)
  {
   Stream decompressedStream = new MemoryStream();
   if (data == null) return decompressedStream;
   try
   {
    var dataStream = new MemoryStream(data);
    using (var zip = ZipFile.Read(dataStream))
    {
     if (zip.Entries.Count > 0)
     {
      zip.Entries.First().Extract(decompressedStream);
      // Extract方法中会操作ms，后续使用时必须先将Stream位置归零，否则会导致后续读取不到任何数据
      // 返回该Stream对象之前进行一次位置归零动作
      decompressedStream.Position = 0;
     }
    }
   }
   catch(Exception ex)
   {
    throw new Exception(ex.Message);
   }
   return decompressedStream;
  }



四.总结：
 以上是对DotNetZip组件的一些解析和方法实例，至于这款组件是不是最好的.NET压缩组件，这个就不做评价。个人在选择组件的时候，首先考虑的是开源，其次是免费，最后再考虑效率和实用性，毕竟在国内的一些情况是所有开发者都清楚的（不提国外是由于我不知道国外的情况）。客户需要降低成本，并且组件要可以进行定制。不过个人认为收费应该是一种趋势，毕竟所有的产品都是需要人员进行维护和开发。以上的博文中有不足之处，还望多多指正。