（转）WP7 断点续传

断点续传其实就是在请求流的时候请求中间流，而不是每次重新从头来过

HttpWebRequest Myrq = (HttpWebRequest)HttpWebRequest.CreateHttp(URL);

Myrq.Headers["Range"] = "bytes=1024-";//设置Range值

这句就是请求1024位置开始到末尾的流

如果Myrq.Headers["Range"] = "bytes=1024-2048";

则表示请求1024到2048位置的数据

有了这个方法，写断点续传就会简单许多了，错略的方法如下

  public void DownFile(string URL, string Filename, ProgressBar Prog)

            //打开上次下载的文件或新建文件

            long lStartPos = 0;

            IsolatedStorageFileStream fs;

            if (IsolatedStorageFile.GetUserStoreForApplication().FileExists(Filename))

                fs = IsolatedStorageFile.GetUserStoreForApplication().OpenFile(Filename, FileMode.Open);

                lStartPos = fs.Length;

                fs.Seek(lStartPos, System.IO.SeekOrigin.Current); //移动文件流中的当前指针

            else

                fs = IsolatedStorageFile.GetUserStoreForApplication().CreateFile(Filename);

                lStartPos = 0;

try

                HttpWebRequest Myrq = (HttpWebRequest)HttpWebRequest.CreateHttp(URL);

                Myrq.Headers["User-Agent"] = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR 1.0.3705)";

                if (lStartPos > 0)

                    Myrq.Headers["Range"] = "bytes=" + lStartPos + "-";//设置Range值

                Myrq.BeginGetResponse(new AsyncCallback((a) =>

                        var myrp = Myrq.EndGetResponse(a);

                        long totalBytes = myrp.ContentLength + fs.Length;

                        this.Dispatcher.BeginInvoke(() => { Prog.Maximum = (int)totalBytes; });

                        Stream st = myrp.GetResponseStream();

                        //Stream so = new FileStream(Filename, FileMode.Create);

                        long totalDownloadedByte = fs.Length;

                        byte[] by = new byte[1024];

                        int osize = st.Read(by, 0, (int)by.Length);

                        while (osize > 0)

                            totalDownloadedByte = osize + totalDownloadedByte;

                            fs.Write(by, 0, osize);

                            this.Dispatcher.BeginInvoke(() => { Prog.Value = (int)totalDownloadedByte; });

                            osize = st.Read(by, 0, (int)by.Length);

                        fs.Close();

                        st.Close();

                        MessageBox.Show("下载完毕!");

                    }), null);

            catch (Exception ex)

                MessageBox.Show("提示" + ex.Message);

http://blog.bryht.net