首先要引用一下类库：using Ionic.Zip;这个类库可以到网上下载。

下面对类库使用的封装方法：

/// <summary>
            /// 得到指定的输入流的ZIP压缩流对象【原有流对象不会改变】
            /// </summary>
            /// <param name="sourceStream"></param>
            /// <returns></returns>
            public static Stream ZipCompress(Stream sourceStream, string entryName = "zip")
            {
                MemoryStream compressedStream = new MemoryStream();
                if (sourceStream != null)
                {
                    long sourceOldPosition = 0;
                    try
                    {
                        sourceOldPosition = sourceStream.Position;
                        sourceStream.Position = 0;
                        using (ZipFile zip = new ZipFile())
                        {
                            zip.AddEntry(entryName, sourceStream);
                            zip.Save(compressedStream);
                            compressedStream.Position = 0;
                        }
                    }
                    catch
                    {
                    }
                    finally
                    {
                        try
                        {
                            sourceStream.Position = sourceOldPosition;
                        }
                        catch
                        {
                        }
                    }
                }
                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="sourceStream"></param>
            /// <returns></returns>
            public static Stream ZipDecompress(byte[] data)
            {
                Stream decompressedStream = new MemoryStream();
                if (data != null)
                {
                    try
                    {
                        MemoryStream dataStream = new MemoryStream(data);
                        using (ZipFile 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
                    {
                    }
                }
                return decompressedStream;
            }
            /// <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)
            {
                try
                {
                    using (ZipFile zip = new ZipFile(Encoding.Default))//设置编码，解决压缩文件时中文乱码
                    {
                        foreach (string path in list)
                        {
                            string fileName = Path.GetFileName(path);//取目录名称
                            //如果是目录
                            if (Directory.Exists(path))
                            {
                                if (IsDirStruct)//按目录结构压缩
                                {
                                    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))//如果是文件
                            {
                                zip.AddFile(path,"imges");
                            }
                        }
                        zip.Save(strZipName);//压缩
                        return true;
                    }
                }
                catch (Exception)
                {
                    return false;
                }
            }
            /// <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)
            {
                try
                {
                    ReadOptions options = new ReadOptions();
                    options.Encoding = Encoding.Default;//设置编码，解决解压文件时中文乱码
                    using (ZipFile zip = ZipFile.Read(strZipPath, options))
                    {
                        foreach (ZipEntry entry in zip)
                        {
                            if (string.IsNullOrEmpty(strUnZipPath))
                            {
                                strUnZipPath = strZipPath.Split('.').First();
                            }
                            if (overWrite)
                            {
                                entry.Extract(strUnZipPath, ExtractExistingFileAction.OverwriteSilently);//解压文件，如果已存在就覆盖
                            }
                            else
                            {
                                entry.Extract(strUnZipPath, ExtractExistingFileAction.DoNotOverwrite);//解压文件，如果已存在不覆盖
                            }
                        }
                        return true;
                    }
                }
                catch (Exception)
                {
                    return false;
                }
            }