详解最好的.NET开源免费ZIP库DotNetZip（.NET组件介绍之三）

 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 ? this.entriessorted : this.entries;
   foreach (zipentry entry in entries)
   {
    this.onsaveentry(current, entry, true);
    entry.write(this.writestream);
    if (this._saveoperationcanceled)
    {
     break;
    }
    current++;
    this.onsaveentry(current, entry, false);
    if (this._saveoperationcanceled)
    {
     break;
    }
    if (entry.includedinmostrecentsave)
    {
     flag |= entry.outputusedzip64.value;
    }
   }
   if (!this._saveoperationcanceled)
   {
    zipsegmentedstream writestream = this.writestream as zipsegmentedstream;
    this._numberofsegmentsformostrecentsave = (writestream != null) ? writestream.currentsegment : 1;
    bool flag2 = zipoutput.writecentraldirectorystructure(this.writestream, entries, this._numberofsegmentsformostrecentsave, this._zip64, this.comment, new zipcontainer(this));
    this.onsaveevent(zipprogresseventtype.saving_aftersavetemparchive);
    this._hasbeensaved = true;
    this._contentschanged = false;
    flag |= flag2;
    this._outputuseszip64 = new bool?(flag);
    if ((this._name != null) && ((this._temporaryfilename != null) || (writestream != null)))
    {
     this.writestream.dispose();
     if (this._saveoperationcanceled)
     {
      return;
     }
     if (this._filealreadyexists && (this._readstream != null))
     {
      this._readstream.close();
      this._readstream = null;
      foreach (zipentry entry2 in entries)
      {
       zipsegmentedstream stream2 = entry2._archivestream as zipsegmentedstream;
       if (stream2 != null)
       {
        stream2.dispose();
       }
       entry2._archivestream = null;
      }
     }
     string path = null;
     if (file.exists(this._name))
     {
      path = this._name + "." + path.getrandomfilename();
      if (file.exists(path))
      {
       this.deletefilewithretry(path);
      }
      file.move(this._name, path);
     }
     this.onsaveevent(zipprogresseventtype.saving_beforerenametemparchive);
     file.move((writestream != null) ? writestream.currenttempname : this._temporaryfilename, this._name);
     this.onsaveevent(zipprogresseventtype.saving_afterrenametemparchive);
     if (path != null)
     {
      try
      {
       if (file.exists(path))
       {
        file.delete(path);
       }
      }
      catch
      {
      }
     }
     this._filealreadyexists = true;
    }
    notifyentriessavecomplete(entries);
    this.onsavecompleted();
    this._justsaved = true;
   }
  }
 }
 finally
 {
  this.cleanupaftersaveoperation();
 }
}

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;
}

 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 ?? defaultencoding,
  _alternateencodingusage = zipoption.always
 };
 if (readprogress != null)
 {
  zf.readprogress += readprogress;
 }
 zf._readstream = (zipstream.position == 0l) ? zipstream : new offsetstream(zipstream);
 zf._readstreamisours = false;
 if (zf.verbose)
 {
  zf._statusmessagetextwriter.writeline("reading from stream...");
 }
 readintoinstance(zf);
 return zf;
}

/// <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);
   }
  }

/// <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
        ? extractexistingfileaction.overwritesilently
        : extractexistingfileaction.donotoverwrite);
     }
     return true;
    }
   }
   catch (exception ex)
   {
    throw new exception(ex.message);
   }
  }

/// <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;
  }

/// <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;
  }