PGIS下载离线map SQLite+WPF

//Task taskDown = new Task(DownTiles);//taskDown.Start();private void DownTiles()        {            double maxX = 138.796586;            double maxY = 24.371022;            double minX = 138.447725;            double minY = 24.086215;            double X0 = -180;            double Y0 = 90;            string tempUrl = "";            HttpWebRequest req = null;            Stream stream = null;            int bufferLen = 1024 * 1024;            int actual;            byte[] buffer = new byte[bufferLen];            for (int i = 9; i < 21; i++)//Level            {                int cmin = Math.Abs(Convert.ToInt32(Math.Floor((X0 - minX) / (256 * MapMethods.GetResoulution(i)))));                int cmax = Math.Abs(Convert.ToInt32(Math.Floor((X0 - maxX) / (256 * MapMethods.GetResoulution(i)))));                int rmin = Math.Abs(Convert.ToInt32(Math.Floor((Y0 - maxY) / (256 * MapMethods.GetResoulution(i)))));                int rmax = Math.Abs(Convert.ToInt32(Math.Floor((Y0 - minY) / (256 * MapMethods.GetResoulution(i)))));                for (int r = rmin; r < rmax; r++)//循环行                {                    for (int c = cmin; c < cmax; c++)//循环列                    {                        //Thread.Sleep(100);                        tempUrl = GetTileUrl(i, r, c);                        req = (HttpWebRequest)WebRequest.Create(tempUrl);                        stream = req.GetResponse().GetResponseStream();                        MemoryStream memoryStream = new MemoryStream();                                                while ((actual = stream.Read(buffer, 0, bufferLen)) > 0)                        {                            memoryStream.Write(buffer, 0, actual);                        }                        memoryStream.Position = 0;                        SaveTile(i, r, c, StreamToBytes2(memoryStream));                                                                    }                }            }        }        private byte[] StreamToBytes2(MemoryStream input)        {            byte[] bytes = new byte[input.Length];            input.Read(bytes, 0, bytes.Length);            return bytes;        }