public void Save(string extPath)
        {
            // https://forums.xamarin.com/discussion/7499/android-content-getexternalfilesdir-is-it-available
            Java.IO.File sd = Android.OS.Environment.ExternalStorageDirectory;
            //FileStream fsOut = File.Create(sd.AbsolutePath + "/Android/data/com.FSoft.are_u_ok_/files/MoodData.zip");
            FileStream fsOut = File.Create(extPath + "/MoodData.zip");
            //https://github.com/icsharpcode/SharpZipLib/wiki/Zip-Samples
            ZipOutputStream zipStream = new ZipOutputStream(fsOut);

            zipStream.SetLevel (3); //0-9, 9 being the highest level of compression
            zipStream.Password = "Br1g1tte";  // optional. Null is the same as not setting. Required if using AES.
            ZipEntry newEntry = new ZipEntry ("Mood.csv");
            newEntry.IsCrypted = true;
            zipStream.PutNextEntry (newEntry);
            // Zip the file in buffered chunks
            // the "using" will close the stream even if an exception occurs
            byte[ ] buffer = new byte[4096];
            string filename = extPath + "/MoodData.csv";
            using (FileStream streamReader = File.OpenRead(filename)) {
                StreamUtils.Copy(streamReader, zipStream, buffer);
            }

            zipStream.CloseEntry ();

            zipStream.IsStreamOwner = true; // Makes the Close also Close the underlying stream
            zipStream.Close ();
        }

        public static void CreateZipFile(string[] filenames, string outputFile)
        {
            // Zip up the files - From SharpZipLib Demo Code
              using (ZipOutputStream s = new ZipOutputStream(File.Create(outputFile)))
              {
            s.SetLevel(9); // 0-9, 9 being the highest level of compression
            byte[] buffer = new byte[4096];
            foreach (string file in filenames)
            {
              ZipEntry entry = new ZipEntry(Path.GetFileName(file));
              entry.DateTime = DateTime.Now;
              s.PutNextEntry(entry);

              using (FileStream fs = File.OpenRead(file))
              {
            int sourceBytes;
            do
            {
              sourceBytes = fs.Read(buffer, 0, buffer.Length);
              s.Write(buffer, 0, sourceBytes);

            }
            while (sourceBytes > 0);
              }
            }
            s.Finish();
            s.Close();
              }
        }

   /// <summary>
 /// 压缩文件夹
 /// </summary>
 /// <param name="dirToZip"></param>
 /// <param name="zipedFileName"></param>
 /// <param name="compressionLevel">压缩率0（无压缩）9（压缩率最高）</param>
 public void ZipDir(string dirToZip, string zipedFileName, int compressionLevel = 9)
 {
     if (Path.GetExtension(zipedFileName) != ".zip")
     {
         zipedFileName = zipedFileName + ".zip";
     }
     using (var zipoutputstream = new ZipOutputStream(File.Create(zipedFileName)))
     {
         zipoutputstream.SetLevel(compressionLevel);
         var crc = new Crc32();
         var fileList = GetAllFies(dirToZip);
         foreach (DictionaryEntry item in fileList)
         {
             var fs = new FileStream(item.Key.ToString(), FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
             var buffer = new byte[fs.Length];
             fs.Read(buffer, 0, buffer.Length);
             // ZipEntry entry = new ZipEntry(item.Key.ToString().Substring(dirToZip.Length + 1));
             var entry = new ZipEntry(Path.GetFileName(item.Key.ToString()))
                              {
                                  DateTime = (DateTime) item.Value,
                                  Size = fs.Length
                              };
             fs.Close();
             crc.Reset();
             crc.Update(buffer);
             entry.Crc = crc.Value;
             zipoutputstream.PutNextEntry(entry);
             zipoutputstream.Write(buffer, 0, buffer.Length);
         }
     }
 }

        public static void ZipFiles(string inputFolderPath, string outputPathAndFile, string password)
        {
            ArrayList ar = GenerateFileList(inputFolderPath); // generate file list
            int TrimLength = (Directory.GetParent(inputFolderPath)).ToString().Length;
            // find number of chars to remove 	// from orginal file path
            TrimLength += 1; //remove '\'
            FileStream ostream;
            byte[] obuffer;
            string outPath = outputPathAndFile;
            ZipOutputStream oZipStream = new ZipOutputStream(File.Create(outPath)); // create zip stream
            if (password != null && password != String.Empty)
                oZipStream.Password = password;
            oZipStream.SetLevel(9); // maximum compression
            ZipEntry oZipEntry;
            foreach (string Fil in ar) // for each file, generate a zipentry
            {
                oZipEntry = new ZipEntry(Fil.Remove(0, TrimLength));
                oZipStream.PutNextEntry(oZipEntry);

                if (!Fil.EndsWith(@"/")) // if a file ends with '/' its a directory
                {
                    ostream = File.OpenRead(Fil);
                    obuffer = new byte[ostream.Length];
                    ostream.Read(obuffer, 0, obuffer.Length);
                    oZipStream.Write(obuffer, 0, obuffer.Length);
                }
            }
            oZipStream.Finish();
            oZipStream.Close();
            oZipStream.Dispose();
        }

        private static void CreateToMemoryStream(IEnumerable<Tuple<string, Stream>> entries, string zipName)
        {
            MemoryStream outputMemStream = new MemoryStream();
            ZipOutputStream zipStream = new ZipOutputStream(outputMemStream);

            zipStream.SetLevel(3); //0-9, 9 being the highest level of compression

            foreach (var entry in entries)
            {
                ZipEntry newEntry = new ZipEntry(entry.Item1);
                newEntry.DateTime = DateTime.Now;

                zipStream.PutNextEntry(newEntry);

                StreamUtils.Copy(entry.Item2, zipStream, new byte[4096]);
                zipStream.CloseEntry();
            }

            zipStream.IsStreamOwner = false;    // False stops the Close also Closing the underlying stream.
            zipStream.Close();          // Must finish the ZipOutputStream before using outputMemStream.

            outputMemStream.Position = 0;
            File.WriteAllBytes(zipName, outputMemStream.ToArray());

            //// Alternative outputs:
            //// ToArray is the cleaner and easiest to use correctly with the penalty of duplicating allocated memory.
            //byte[] byteArrayOut = outputMemStream.ToArray();

            //// GetBuffer returns a raw buffer raw and so you need to account for the true length yourself.
            //byte[] byteArrayOut = outputMemStream.GetBuffer();
            //long len = outputMemStream.Length;
        }

 private void zip(string strFile, ZipOutputStream s, string staticFile)
 {
     if (strFile[strFile.Length - 1] != Path.DirectorySeparatorChar) strFile += Path.DirectorySeparatorChar;
     Crc32 crc = new Crc32();
     string[] filenames = Directory.GetFileSystemEntries(strFile);
     foreach (string file in filenames)
     {
         if (Directory.Exists(file))
         {
             zip(file, s, staticFile);
         }
         else // 否则直接压缩文件
         {
             //打开压缩文件
             FileStream fs = File.OpenRead(file);
             byte[] buffer = new byte[fs.Length];
             fs.Read(buffer, 0, buffer.Length);
             string tempfile = file.Substring(staticFile.LastIndexOf("\\") + 1);
             ZipEntry entry = new ZipEntry(tempfile);
             entry.DateTime = DateTime.Now;
             entry.Size = fs.Length;
             fs.Close();
             crc.Reset();
             crc.Update(buffer);
             entry.Crc = crc.Value;
             s.PutNextEntry(entry);
             s.Write(buffer, 0, buffer.Length);
         }
     }
 }

 public static  void Zip(string strFile, string strZipFile)
 {
     Crc32 crc1 = new Crc32();
     ZipOutputStream stream1 = new ZipOutputStream(File.Create(strZipFile));
     try
     {
         stream1.SetLevel(6);
         FileStream stream2 = File.OpenRead(strFile);
         byte[] buffer1 = new byte[stream2.Length];
         stream2.Read(buffer1, 0, buffer1.Length);
         ZipEntry entry1 = new ZipEntry(strFile.Split(new char[] { '\\' })[strFile.Split(new char[] { '\\' }).Length - 1]);
         entry1.DateTime = DateTime.Now;
         entry1.Size = stream2.Length;
         stream2.Close();
         crc1.Reset();
         crc1.Update(buffer1);
         entry1.Crc = crc1.Value;
         stream1.PutNextEntry(entry1);
         stream1.Write(buffer1, 0, buffer1.Length);
     }
     catch (Exception exception1)
     {
         throw exception1;
     }
     finally
     {
         stream1.Finish();
         stream1.Close();
         stream1 = null;
         crc1 = null;
     }
 }

 public void Decompress(ZipEntry file, Stream str) {
   int size;
   while (true) {
     size = zipIn.Read(buf, 0, buf.Length); if (size <= 0) break;
     str.Write(buf, 0, (int)size);
   }
 }

        // See this link for details on zipping using SharpZipLib:  https://github.com/icsharpcode/SharpZipLib/wiki/Zip-Samples#wiki-anchorCreate
        public void Write(Cookbookology.Domain.Cookbook cookbook, Stream outputStream)
        {
            if (cookbook == null) throw new ArgumentNullException("cookbook");
            if (outputStream == null) throw new ArgumentNullException("outputStream");

            var converter = new MyCookbookConverter();
            var mcb = converter.ConvertFromCommon(cookbook);

            var ms = new MemoryStream();
            var s = new XmlSerializer(typeof(Cookbook));
            s.Serialize(ms, mcb);
            ms.Position = 0; // reset to the start so that we can write the stream

            // Add the cookbook as a single compressed file in a Zip
            using (var zipStream = new ZipOutputStream(outputStream))
            {
                zipStream.SetLevel(3); // compression
                zipStream.UseZip64 = UseZip64.Off; // not compatible with all utilities and OS (WinXp, WinZip8, Java, etc.)

                var entry = new ZipEntry(mcbFileName);
                entry.DateTime = DateTime.Now;

                zipStream.PutNextEntry(entry);
                StreamUtils.Copy(ms, zipStream, new byte[4096]);
                zipStream.CloseEntry();

                zipStream.IsStreamOwner = false; // Don't close the outputStream (parameter)
                zipStream.Close();
            }
        }

        public byte[] diskLess()
        {
            MemoryStream ms = new MemoryStream();
            StreamWriter sw = new StreamWriter(ms);
            sw.WriteLine("HELLO!");
            sw.WriteLine("I WANT TO SAVE THIS FILE AS A .TXT FILE WITHIN TWO FOLDERS");
            sw.Flush(); //This is required or you get a blank text file :)
            ms.Position = 0;

            // create the ZipEntry archive from the txt file in memory stream ms
            MemoryStream outputMS = new System.IO.MemoryStream();

            ZipOutputStream zipOutput = new ZipOutputStream(outputMS);

            ZipEntry ze = new ZipEntry(@"dir1/dir2/whatever.txt");
            zipOutput.PutNextEntry(ze);
            zipOutput.Write(ms.ToArray(), 0, Convert.ToInt32(ms.Length));
            zipOutput.Finish();
            zipOutput.Close();
            byte[] byteArrayOut = outputMS.ToArray();
            outputMS.Close();

            ms.Close();

            return byteArrayOut;

        }

 public ClsZipFileItem(string zipPath, ZipEntry entry)
     : base(entry.Name, entry.DateTime)
 {
     _path = entry.Name;
     _entry = entry;
     _zipPath = zipPath;
 }

		private void CompressFilesToOneZipFile(ICollection<string> inputPaths, string zipFilePath)
		{
			Log.LogMessage(MessageImportance.Normal, "Zipping " + inputPaths.Count + " files to zip file " + zipFilePath);

			using (var fsOut = File.Create(zipFilePath)) // Overwrites previous file
			{
				using (var zipStream = new ZipOutputStream(fsOut))
				{
					foreach (var inputPath in inputPaths)
					{
						zipStream.SetLevel(9); // Highest level of compression

						var inputFileInfo = new FileInfo(inputPath);

						var newEntry = new ZipEntry(inputFileInfo.Name) { DateTime = inputFileInfo.CreationTime };
						zipStream.PutNextEntry(newEntry);

						var buffer = new byte[4096];
						using (var streamReader = File.OpenRead(inputPath))
						{
							ICSharpCode.SharpZipLib.Core.StreamUtils.Copy(streamReader, zipStream, buffer);
						}

						zipStream.CloseEntry();
					}
					zipStream.IsStreamOwner = true;
					zipStream.Close();
				}
			}
		}

        /// <summary>
        /// Compress an string using ZIP
        /// </summary>
        /// <param name="xml"></param>
        /// <returns></returns>
        public static byte[] CompressContent(string contentToZip)
        {

            System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
            byte[] buff = encoding.GetBytes(contentToZip);

            try
            {
                using (MemoryStream stream = new MemoryStream())
                {
                    using (ZipOutputStream zipout = new ZipOutputStream(stream))
                    {
                        zipout.SetLevel(9);
                        ZipEntry entry = new ZipEntry("zipfile.zip");
                        entry.DateTime = DateTime.Now;
                        zipout.PutNextEntry(entry);
                        zipout.Write(buff, 0, buff.Length);
                        zipout.Finish();
                        byte[] outputbyte = new byte[(int)stream.Length];
                        stream.Position = 0;
                        stream.Read(outputbyte, 0, (int)stream.Length);
                        return outputbyte;
                    }

                }
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                return null;
            }
        }

        public override void ExecuteResult(ControllerContext context)
        {
            string fileName = Path.GetTempFileName();

            var response = context.HttpContext.Response;

            using (var zipOutputStream = new ZipOutputStream(new FileStream(fileName, FileMode.OpenOrCreate)))
            {
                zipOutputStream.SetLevel(0);
                foreach (var photo in Photos)
                {
                    //FileInfo fileInfo = new FileInfo(photo.MediaFilePath);
                    ZipEntry entry = new ZipEntry(Tag.Name + @"\" + photo.Id + ".jpg");
                    zipOutputStream.PutNextEntry(entry);
                    using (FileStream fs = System.IO.File.OpenRead(photo.MediaFilePath))
                    {

                        byte[] buff = new byte[1024];
                        int n = 0;
                        while ((n = fs.Read(buff, 0, buff.Length)) > 0)
                            zipOutputStream.Write(buff, 0, n);
                    }
                }
                zipOutputStream.Finish();
            }

            System.IO.FileInfo file = new System.IO.FileInfo(fileName);
            response.Clear();
            response.AddHeader("Content-Disposition", "attachment; filename=" + "Photos.zip");
            response.AddHeader("Content-Length", file.Length.ToString());
            response.ContentType = "application/octet-stream";
            response.WriteFile(file.FullName);
            response.End();
            System.IO.File.Delete(fileName);
        }

        private static void CompressFolder(string path, ZipOutputStream zipStream)
        {
            string[] files = Directory.GetFiles(path);
            foreach (string filename in files)
            {
                FileInfo fi = new FileInfo(filename);

                int offset = _root.Length + 3;
                string entryName = filename.Substring(offset);
                entryName = ZipEntry.CleanName(entryName);
                ZipEntry newEntry = new ZipEntry(entryName);
                newEntry.DateTime = fi.LastWriteTime;

                newEntry.Size = fi.Length;
                zipStream.PutNextEntry(newEntry);

                byte[] buffer = new byte[4096];
                using (FileStream streamReader = File.OpenRead(filename))
                {
                    StreamUtils.Copy(streamReader, zipStream, buffer);
                }
                zipStream.CloseEntry();
            }
            string[] folders = Directory.GetDirectories(path);
            foreach (string folder in folders)
            {
                CompressFolder(folder, zipStream);
            }
        }

        // Recurses down the folder structure
        //
        private void CompressFile(string filename, ZipOutputStream zipStream, int fileOffset)
        {
            var fi = new FileInfo(filename);

            var entryName = Path.GetFileName(filename); // Makes the name in zip based on the folder
            entryName = ZipEntry.CleanName(entryName); // Removes drive from name and fixes slash direction
            var newEntry = new ZipEntry(entryName);
            newEntry.DateTime = fi.LastWriteTime; // Note the zip format stores 2 second granularity

            // Specifying the AESKeySize triggers AES encryption. Allowable values are 0 (off), 128 or 256.
            //   newEntry.AESKeySize = 256;

            // To permit the zip to be unpacked by built-in extractor in WinXP and Server2003, WinZip 8, Java, and other older code,
            // you need to do one of the following: Specify UseZip64.Off, or set the Size.
            // If the file may be bigger than 4GB, or you do not need WinXP built-in compatibility, you do not need either,
            // but the zip will be in Zip64 format which not all utilities can understand.
            //   zipStream.UseZip64 = UseZip64.Off;
            newEntry.Size = fi.Length;

            zipStream.PutNextEntry(newEntry);

            // Zip the file in buffered chunks
            // the "using" will close the stream even if an exception occurs
            var buffer = new byte[4096];
            using (var streamReader = File.OpenRead(filename))
            {
                StreamUtils.Copy(streamReader, zipStream, buffer);
            }
            zipStream.CloseEntry();
        }

        public void CreateZipFile(string[] straFilenames, string strOutputFilename)
        {
            Crc32 crc = new Crc32();
            ZipOutputStream zos = new ZipOutputStream(File.Create(strOutputFilename));

            zos.SetLevel(m_nCompressionLevel);

            foreach (string strFileName in straFilenames)
            {
                FileStream fs = File.OpenRead(strFileName);

                byte[] buffer = new byte[fs.Length];
                fs.Read(buffer, 0, buffer.Length);
                ZipEntry entry = new ZipEntry(GetFileNameWithoutDrive(strFileName));

                entry.DateTime = DateTime.Now;

                entry.Size = fs.Length;
                fs.Close();

                crc.Reset();
                crc.Update(buffer);

                entry.Crc  = crc.Value;

                zos.PutNextEntry(entry);

                zos.Write(buffer, 0, buffer.Length);
            }

            zos.Finish();
            zos.Close();
        }

        public void ZipFile(string FileToZip, string ZipedFile, int CompressionLevel, int BlockSize)
        {
            //如果文件没有找到，则报错
            if (!System.IO.File.Exists(FileToZip))
            {
                throw new System.IO.FileNotFoundException("The specified file " + FileToZip + " could not be found. Zipping aborderd");
            }

            System.IO.FileStream StreamToZip = new System.IO.FileStream(FileToZip, System.IO.FileMode.Open, System.IO.FileAccess.Read);
            System.IO.FileStream ZipFile = System.IO.File.Create(ZipedFile);
            ZipOutputStream ZipStream = new ZipOutputStream(ZipFile);
            ZipEntry ZipEntry = new ZipEntry("ZippedFile");
            ZipStream.PutNextEntry(ZipEntry);
            ZipStream.SetLevel(CompressionLevel);
            byte[] buffer = new byte[BlockSize];
            System.Int32 size = StreamToZip.Read(buffer, 0, buffer.Length);
            ZipStream.Write(buffer, 0, size);
            try
            {
                while (size < StreamToZip.Length)
                {
                    int sizeRead = StreamToZip.Read(buffer, 0, buffer.Length);
                    ZipStream.Write(buffer, 0, sizeRead);
                    size += sizeRead;
                }
            }
            catch (System.Exception ex)
            {
                throw ex;
            }
            ZipStream.Finish();
            ZipStream.Close();
            StreamToZip.Close();
        }

 public Stream GetInputStream(ZipEntry entry)
 {
     if (zipArchive == null)
         throw new InvalidDataException("Zip File is closed");
     Stream s = zipArchive.GetInputStream(entry);
     return s;
 }

        /// <summary>
        /// ファイルを圧縮
        /// </summary>
        /// <param name="filename">ファイル名フルパス</param>
        /// <param name="offsetFolderName">圧縮時のルートフォルダのフルパス</param>
        /// <param name="zipStream">圧縮先のZipStream</param>
        public static void CompressFile(string filename, string offsetFolderName, ZipOutputStream zipStream)
        {
            //フォルダのオフセット値を取得
            var folderOffset = offsetFolderName.Length + (offsetFolderName.EndsWith("\\") ? 0 : 1);

            //ファイル名の余計なパスを消す
            string entryName = filename.Substring(folderOffset);
            entryName = ZipEntry.CleanName(entryName);

            //圧縮するファイルを表示←非常に良くない
            Console.WriteLine(entryName);

            //ファイル情報書き込み
            var fi = new FileInfo(filename);
            var newEntry = new ZipEntry(entryName)
            {
                DateTime = fi.LastWriteTime,
                Size = fi.Length,
            };
            zipStream.PutNextEntry(newEntry);

            //ファイル内容書き込み
            var buffer = new byte[4096];
            using (var streamReader = File.OpenRead(filename))
            {
                StreamUtils.Copy(streamReader, zipStream, buffer);
            }

            zipStream.CloseEntry();
        }