Zip 压缩问题件，获取真实扩展名

var _ZIP = new System.IO.Compression.ZipArchive(Request.Files[].InputStream);

foreach (var element in _ZIP.Entries)
{
    using (System.IO.StreamReader _ddd = new System.IO.StreamReader(element.Open()))
    {
        string _Text = _ddd.ReadToEnd();

    }

    using (System.IO.BinaryReader _ddd = new System.IO.BinaryReader(element.Open()))
    {
        string bx = " ";
        byte buffer;
        buffer = r.ReadByte();
        bx = buffer.ToString();
        buffer = r.ReadByte();
        bx += buffer.ToString();

            //bx == 255216 jpg 파일
    }
}

        static void Main(string[] args)
        {

            string str = string.Empty;
            str= Console.ReadLine();
            Console.WriteLine("length:" + str.Length);
            str=ToZip(str);
            Console.WriteLine("ToZip:" + str);
            Console.WriteLine("length:" + str.Length);
            str= ToUnzip(str);
            Console.WriteLine("ToUnzip:" + str);
            Console.WriteLine("length:" + str.Length);
            Console.Read();
        }

        static string ToZip(string _str) {

            string result = string.Empty;
            byte[] bString = Encoding.UTF8.GetBytes(_str);
            using (var msi = new System.IO.MemoryStream(bString))
            using (var mso = new System.IO.MemoryStream())
            {
                using (var gs = new System.IO.Compression.GZipStream(mso, System.IO.Compression.CompressionMode.Compress))
                {
                    byte[] bTemp = new byte[];
                    int count;
                    while ((count = msi.Read(bTemp, , bTemp.Length)) != )
                    {
                        gs.Write(bTemp, , count);
                    }
                }
                result= System.Convert.ToBase64String(mso.ToArray());
            }
            return result;
        }
        static string ToUnzip(string _str)
        {
            string result = string.Empty;
            byte[] bString = System.Convert.FromBase64String(_str);
            using (var msi = new System.IO.MemoryStream(bString))
            using (var mso = new System.IO.MemoryStream())
            {
                using (var gs = new System.IO.Compression.GZipStream(msi, System.IO.Compression.CompressionMode.Decompress))
                {
                    byte[] bTemp = new byte[];
                    int count;
                    while ((count = gs.Read(bTemp, , bTemp.Length)) != )
                    {
                        mso.Write(bTemp, , count);
                    }
                }
                result= Encoding.UTF8.GetString(mso.ToArray());
            }

            return result;
        }