Stream 与 byte[] 互转

        public byte[] StreamToBytes(Stream stream)
        {
            byte[] bytes = new byte[stream.Length];
            stream.Read(bytes, 0, bytes.Length);            
            stream.Seek(0, SeekOrigin.Begin);// 设置当前流的位置为流的开始
            return bytes;
        }
        public Stream BytesToStream(byte[] bytes)
        {
            Stream stream = new MemoryStream(bytes);
            return stream;
        }