1         /// <summary>
  2         /// 下载并保存文件
  3         /// </summary>
  4         /// <param name="waveID">主键</param>
  5         /// <param name="saveName">文件名</param>
  8         /// <param name="folderName">文件夹名称</param>
  9         /// <param name="speed">限速</param>
 10         /// <param name="callBackMethod">回调</param>
 11         /// <returns></returns>
 12         public int DownloadAndSaveAs(string waveID, string saveName, string folderName, int speed, SetTextCallBack callBackMethod)
 13         {
 14             if (string.IsNullOrWhiteSpace(waveID))
 15                 return -1;
 16 
 17             using (WebClient webClient = new WebClient())
 18             {
 19                 try
 20                 {
 21                     string savePath = "C:\\"+ folderName+ "\\";
 22                     if (!Directory.Exists(savePath))
 23                     {
 24                         Directory.CreateDirectory(savePath);
 25                     }
 26                     using (FileStream fs = new FileStream(savePath + saveName, FileMode.Create, FileAccess.Write))
 27                     {
 28                         try
 29                         {
 30                             string url =string.Format(  "Http://www.文件下载路径.com?waveID={0}",waveID);
 31                             HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
 32 
 33                             using (var response = (HttpWebResponse)request.GetResponse())
 34                             using (var stream = response.GetResponseStream())
 35                             {
 36                                 int blockSize = 4096;//每次读取的字节数，不固定
 37                                 byte[] buffer = new byte[blockSize];
 38                                 int read = 0;//每次读取后返回的下一次 的坐标位置，当没有数据时是-1
 39                                 long total_read = 0;//已经读取到的字节数总和
 40                                 DateTime begin = DateTime.Now;
 41                                 
 42                                 while ((read = stream.Read(buffer, 0, buffer.Length)) > 0)
 43                                 {
 44                                     total_read += blockSize;      
 45                                     double totalSeconds=DateTime.Now.Subtract(begin).TotalSeconds;
 46                                     double byteper = total_read / totalSeconds;//[字节总数]除以[所花时间总秒数]=每秒获取的字节数
 47 
 48                                     if (double.IsInfinity(byteper))
 49                                     {
 50                                         //排除byteper正无穷的情况
 51                                         fs.Write(buffer, 0, buffer.Length);
 52                                         continue;
 53                                     }
 54                                     else
 55                                     {
 56                                         double speedPer = byteper / 1024;//单位转换得到千字节
 57                                         if (speedPer >= speed)//speed为我们设置的限速字段，单位kb
 58                                         {
 59                                             //下面的逻辑是通过：现实速度-限速=超速部分，通过超速部分计算要让线程休眠时长。
 60                                             double tempData = speedPer - speed;
 61                                             if (tempData < 1) tempData = 1;
 62                                             int sleepMS = Convert.ToInt32(tempData * (1000 / speed) + 100);//1000除以速度得到“每KB消耗的毫秒数”，100是一个自定义值，更好的限制下载速度
 63                                             if (sleepMS > 1000)
 64                                             {
 65                                                 sleepMS = 1000;//有时下载峰值会超大，导致休眠很长，所以强制设为最多休眠一秒。
 66                                             }
 67                                             else
 68                                             {
 69                                                 if (total_read % 112 == 0)//取模只用于降低重写文本框的频率
 70                                                 {
 71                                                     if (callBackMethod != null)
 72                                                     {
 73                                                         callBackMethod(string.Format("下载速度：{0}KB/s，休眠周期：{1} ms", speedPer.ToString("F"), sleepMS));
 74                                                     }
 75                                                 }
 76                                             }
 77                                             System.Threading.Thread.Sleep(sleepMS);  // 休眠实现限速
 78                                         }
 79                                         else
 80                                         {
 81                                             if (total_read % 198 == 0)
 82                                             {
 83                                                 if (callBackMethod != null)
 84                                                 {
 85                                                     callBackMethod(string.Format("下载速度：{0}KB/s，休眠周期：{1} ms", speedPer.ToString("F"), 0));
 86                                                 }
 87                                             }
 88                                         
 89                                         }
 90                                         fs.Write(buffer, 0, buffer.Length);
 91                                     }
 92                                 }                                 
 93                             }                            
 94                             return 1;
 95                         }
 96                         catch (Exception e)
 97                         {
 98                             return -1;
 99                         }
100                     }
101                 }
102                 catch (Exception ex)
103                 {
104                     return -1;
105                 }
106             }
107         }