C#文件下载（实现断点续传）
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1 public class WebDown
2 {
4 /// 下载文件方法
6 /// 文件保存路径和文件名
7 /// 返回服务器文件名
9 public static bool DeownloadFile(string sourceFile, string desFile)
10 {
11 bool flag = false;
12 long SPosition = 0;
13 FileStream FStream = null;
14 Stream myStream = null;
15 string fileName = sourceFile.Substring(sourceFile.LastIndexOf(@"/") + 1);
16 if (desFile.EndsWith("\\"))
17 {
18 desFile = desFile + fileName;
19 }
20 else
21 {
22 desFile = desFile + "\\" + fileName;
23 }
24 try
25 {
26 //判断要下载的文件夹是否存在
27 if (File.Exists(desFile))
28 {
29 //打开上次下载的文件
30 FStream = File.OpenWrite(desFile);
31 //获取已经下载的长度
32 SPosition = FStream.Length;
33 long serverFileLength = GetHttpLength(sourceFile);
34 if (SPosition == serverFileLength)
35 {//文件是完整的，直接结束下载任务
36 return true;
37 }
38 FStream.Seek(SPosition, SeekOrigin.Current);
39 }
40 else
41 {
42 //文件不保存创建一个文件
43 FStream = new FileStream(desFile, FileMode.Create);
44 SPosition = 0;
45 }
46 //打开网络连接
47 HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(sourceFile);
48 if (SPosition > 0)
49 {
50 myRequest.AddRange(SPosition); //设置Range值
51 }
52 //向服务器请求,获得服务器的回应数据流
53 myStream = myRequest.GetResponse().GetResponseStream();
54 //定义一个字节数据
55 byte[] btContent = new byte[512];
56 int intSize = 0;
57 intSize = myStream.Read(btContent, 0, 512);
58 while (intSize > 0)
59 {
60 FStream.Write(btContent, 0, intSize);
61 intSize = myStream.Read(btContent, 0, 512);
62 }
63 flag = true; //返回true下载成功
64 }
65 catch (Exception ex)
66 {
67 SysLog.WriteTxtLog("下载文件时异常：" + ex.Message);
68 }
69 finally
70 {
71 //关闭流
72 if (myStream != null)
73 {
74 myStream.Close();
75 myStream.Dispose();
76 }
77 if (FStream != null)
78 {
79 FStream.Close();
80 FStream.Dispose();
81 }
82 }
83 return flag;
84 }
85 static long GetHttpLength(string url)
86 {
87 long length = 0;
88 try
89 {
90 var req = (HttpWebRequest)WebRequest.CreateDefault(new Uri(url));
91 req.Method = "HEAD";
92 req.Timeout = 5000;
93 var res = (HttpWebResponse)req.GetResponse();
94 if (res.StatusCode == HttpStatusCode.OK)
95 {
96 length = res.ContentLength;
97 }
98 res.Close();
99 return length;
100 }
101 catch (WebException wex)
102 {
103 return 0;
104 }
105 }
106 }
该文章在 2021/1/29 21:58:11 编辑过 |
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