我在网上找到这个

 public static string DeCompress(string fileName, string dirPath)
        {
            string iid = string.Empty;
            using (Stream source = File.OpenRead(fileName))
            {
                using (Stream destination = new MemoryStream())
                {
                    using (GZipStream input = new GZipStream(source, CompressionMode.Decompress, true))
                    {

                        byte[] bytes = new byte[4096 * 100];
                        int n = input.Read(bytes, 0, bytes.Length);

                        if (n > 0)
                        {
                            destination.Write(bytes, 0, n);
                        }
                    }
                    destination.Flush();
                    destination.Position = 0;

                    
                    DeSerializeFiles(destination, dirPath);
                }
            }

            return iid;
        }



        private static void DeSerializeFiles(Stream s, string dirPath)
        {
            BinaryFormatter b = new BinaryFormatter();
           
            ArrayList list = (ArrayList)b.Deserialize(s);

            foreach (SerializeFileInfo f in list)
            {
                string newName = dirPath + Path.GetFileName(f.FileName);
                using (FileStream fs = new FileStream(newName, FileMode.Create, FileAccess.Write))
                {
                    fs.Write(f.FileBuffer, 0, f.FileBuffer.Length);
                    fs.Close();
                }
            }
        }

标红出有异常，不知道怎么解决了