Create Zip file in MemoryStream

今天项目有一新需求，需要从数据库中将文件打包，在客户端（BS架构）下载。由于系统将所有上传的文件都存储在数据库，这就牵涉到两点，首先要把数据库中的数据读出来，然后再利用ICSharpCode将文件打包。

 

由于是BS架构，因而不可能将数据库中的文件存储为某个临时文件，再进行打包，所以只好把文件以MemoryStream形式写入到Zip包中，同时需要注意的是，ZipEntry是不好重复的，如果碰到相同的文件名，是需要加以区分的，比如aaa.jpg，aaa(1).jpg，aaa(2).jpg。

 

在写入Zip包前，还需要用CRC来格式化buffer，就像是写到磁盘一样。

 

最后通过Response.OutputStream来实现客户端下载Zip文件。还有就是别忘记把Stream关闭。

 

 

下面这段代码就是实现了这样的需求。

 

 

            #region Initialize

            MemoryStream ziparchive = new MemoryStream();
            ZipOutputStream MyZipStream = new ZipOutputStream(ziparchive);
            // This is required inorder to close the zip archive and leave the stream intact
            MyZipStream.IsStreamOwner = false;
            // Set the compression level
            MyZipStream.SetLevel(6);

            bool? IsDefault = null;
            bool? IsThumbnail = null;
            if (ConvertClass.BooleanWrapper(rbtDownloadOptions.SelectedValue))
            {
                IsDefault = true;
            }
            if (!ConvertClass.BooleanWrapper(rbtDownloadOptions.SelectedValue))
            {
                IsThumbnail = true;
            }

            FileNameList.Clear();

            #endregion

            #region Get gift picture file into zip file

            XmlDocument mXMLDocument = new XmlDocument();
            mXMLDocument.LoadXml(GiftIDs);
            XmlNodeList NodeList = mXMLDocument.SelectNodes("//items/item");

            foreach (XmlNode idNode in NodeList)
            {
                #region Get image stream

                // Get Image Data
                DataSet ds = DataSource;

                if (ds.Tables.Count == 0)
                {
                    continue;
                }

                if (ds.Tables[0].Rows.Count == 0)
                {
                    continue;
                }

                DataRow dr = ds.Tables[0].Rows[0];

                #endregion

                // This is how to get the data out of the stream
                byte[] buffer = (byte[])dr["GiftPicture"];
                MemoryStream stream = new MemoryStream(buffer);

                // Create the zip entry
                string entryName = string.Empty;
                if (ConvertClass.BooleanWrapper(rbtFileNameOptions.SelectedValue))
                {
                    GiftEntity CurrentGift = new GiftEntity();
                    CurrentGift.GiftID = ConvertClass.Int32Wrapper(idNode.Attributes["id"].Value);
                    CurrentGift = DataSource;

                    entryName = CurrentGift.GiftReference + GetFileExtensionName(dr["GiftPictureFileName"].ToString());
                }
                else
                {
                    entryName = dr["GiftPictureFileName"].ToString();
                }
                ZipEntry entry = new ZipEntry(GetNonDuplicatedNameOfFile(entryName, 1));
                entry.DateTime = DateTime.Now;
                entry.Size = buffer.Length;

                // Use CRC to format the buffer
                Crc32 objCrc32 = new Crc32();
                objCrc32.Reset();
                objCrc32.Update(buffer);
                entry.Crc = objCrc32.Value;

                // Write the zip file
                MyZipStream.PutNextEntry(entry);
                MyZipStream.Write(buffer, 0, buffer.Length);
                stream.Close();
            }

            #endregion

            #region Generate zip file

            MyZipStream.Finish();
            MyZipStream.Close();

            // We have created the zip file and now it's time to serve it
            Response.Clear();
            Response.AddHeader("Content-Disposition", "attachment; filename=" + txtZIPFileName.Text + ".zip");
            Response.ContentType = "application/x-zip-compressed";


            byte[] ZipBuffer = new byte[ziparchive.Length - 1];
            ZipBuffer = ziparchive.GetBuffer();

            Response.OutputStream.Write(ZipBuffer, 0, Convert.ToInt32(ziparchive.Length));
            Response.End();

            MyZipStream.Close();

            #endregion