c#解压问题求帮助

讨教个问题c#解压问题，本人在pb中压缩的。前4个字节存的文件原始长度+zlib  压缩的内容，合并后的在c#中怎么解压？
本人用的调用外部zlib.dll老报 -3错误

}
        [DllImport("ZLIB1.DLL", EntryPoint = "uncompress")]
        private static extern int uncompress(ref byte[] uncompr, ref uint uncomprlen, ref   byte[] compr, uint lcomp);
        private int of_uncompress(ref object ob, int lx)
        {
            /// <summary>This is the important function that will perform the conversion</summary>
            uint ll_UncompressedLen, ll_UncompressLen = 0;int ll_Return;
        Byte[] lblb_Uncompressed, ablb_uncompress,b1,b2;
            ablb_uncompress = Serialize(ob);
            b1 = new byte[4];
            b1=ablb_uncompress.Take(4).ToArray();
            b2= ablb_uncompress.Skip(4).ToArray();
            //ll_UncompressedLen = (int)Deserialize(b1);
            ll_UncompressedLen = 100000;// BitConverter.ToInt32(b1,0);
            //ablb_uncompress = blobmid(ablb_uncompress, 5);
            //ll_UncompressLen = len(ablb_uncompress);
            lblb_Uncompressed =new byte[ll_UncompressedLen];
            ll_UncompressLen = 10000;// b2.Length;
            ll_Return = uncompress(ref lblb_Uncompressed, ref ll_UncompressedLen,ref   b2,  ll_UncompressLen );
            ob = Deserialize(lblb_Uncompressed);
   return ll_Return;
            }
        ///<summary> 
        /// 序列化 
        /// </summary> 
        /// <param name="data">要序列化的对象</param> 
        /// <returns>返回存放序列化后的数据缓冲区</returns> 
        public static byte[] Serialize(object data)
        {
            BinaryFormatter formatter = new BinaryFormatter();
            MemoryStream rems = new MemoryStream();
            formatter.Serialize(rems, data);
            return rems.GetBuffer();
        }
        /// <summary> 
        /// 反序列化 
        /// </summary> 
        /// <param name="data">数据缓冲区</param> 
        /// <returns>对象</returns> 
        public static object Deserialize(byte[] data)
        {
            BinaryFormatter formatter = new BinaryFormatter();
            MemoryStream rems = new MemoryStream(data);
            data = null;
            //rems.Position = 0;
            //formatter.posi
            rems.Seek(0, SeekOrigin.Begin);
            
            return formatter.Deserialize(rems);
        }