PGIS下载离线地图 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;
        }