C#http下载文件

特点：

（1）下载文件加上downloading后缀,下载完成再去掉后缀，

（2）含有通知下载进度事件

（3）断点续传

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public class DownloadHelper {     private int ByteSize = 1024;       /// <summary>     /// 下载中的后缀，下载完成去掉     /// </summary>     private const string Suffix = ".downloading";       public event Action<int> ShowDownloadPercent;       /// <summary>     /// Http方式下载文件     /// </summary>     /// <param name="url">http地址</param>     /// <param name="localfile">本地文件</param>     /// <returns></returns>     public int DownloadFile(string url, string localfile)     {         int ret = 0;         string localfileReal = localfile;         string localfileWithSuffix = localfileReal + Suffix;           try         {             long startPosition = 0;             FileStream writeStream = null;               if (string.IsNullOrEmpty(url) || string.IsNullOrEmpty(localfileReal))                 return 1;               //取得远程文件长度             long remoteFileLength = GetHttpLength(url);             if (remoteFileLength == 0)                 return 2;               if (File.Exists(localfileReal))                 return 0;               //判断要下载的文件是否存在             if (File.Exists(localfileWithSuffix))             {                 writeStream = File.OpenWrite(localfileWithSuffix);                 startPosition = writeStream.Length;                 if (startPosition > remoteFileLength)                 {                     writeStream.Close();                     File.Delete(localfileWithSuffix);                     writeStream = new FileStream(localfileWithSuffix, FileMode.Create);                 }                 else if (startPosition == remoteFileLength)                 {                     DownloadFileOk(localfileReal, localfileWithSuffix);                     writeStream.Close();                     return 0;                 }                 else                     writeStream.Seek(startPosition, SeekOrigin.Begin);             }             else                 writeStream = new FileStream(localfileWithSuffix, FileMode.Create);               HttpWebRequest req = null;             HttpWebResponse rsp = null;             try             {                 req = (HttpWebRequest)HttpWebRequest.Create(url);                 if (startPosition > 0)                     req.AddRange((int)startPosition);                   rsp = (HttpWebResponse)req.GetResponse();                 using (Stream readStream = rsp.GetResponseStream())                 {                     byte[] btArray = new byte[ByteSize];                     long currPostion = startPosition;                     int contentSize = 0;                     while ((contentSize = readStream.Read(btArray, 0, btArray.Length)) > 0)                     {                         writeStream.Write(btArray, 0, contentSize);                         currPostion += contentSize;                           if (ShowDownloadPercent != null)                             ShowDownloadPercent((int)(currPostion * 100 / remoteFileLength));                     }                 }             }             catch (Exception ex)             {                 Log.Info("获取远程文件失败！exception：\n" + ex.ToString());                 ret = 3;             }             finally             {                 if (writeStream != null)                     writeStream.Close();                 if (rsp != null)                     rsp.Close();                 if (req != null)                     req.Abort();                   if (ret == 0)                     DownloadFileOk(localfileReal, localfileWithSuffix);             }         }         catch (Exception ex)         {             Log.Info("获取远程文件失败！exception：\n" + ex.ToString());             ret = 4;         }           return ret;     }       /// <summary>     /// 下载完成     /// </summary>     private void DownloadFileOk(string localfileReal, string localfileWithSuffix)     {         try         {             //去掉.downloading后缀             FileInfo fi = new FileInfo(localfileWithSuffix);             fi.MoveTo(localfileReal);         }         catch (Exception ex)         {             Log.Error(ex.ToString());         }         finally         {             //通知完成             if (ShowDownloadPercent != null)                 ShowDownloadPercent(100);         }     }       // 从文件头得到远程文件的长度     private long GetHttpLength(string url)     {         long length = 0;         HttpWebRequest req = null;         HttpWebResponse rsp = null;         try         {             req = (HttpWebRequest)HttpWebRequest.Create(url);             rsp = (HttpWebResponse)req.GetResponse();             if (rsp.StatusCode == HttpStatusCode.OK)                 length = rsp.ContentLength;         }         catch (Exception ex)         {             Log.Info("获取远程文件大小失败！exception：\n" + ex.ToString());         }         finally         {             if (rsp != null)                 rsp.Close();             if (req != null)                 req.Abort();         }           return length;     }   }

　　

 

参考：http://www.cnblogs.com/hayden/archive/2012/04/26/2472815.html  纯下载

参考：https://www.jb51.net/article/57068.htm 纯下载