如何以编程方式从网站下载文件c＃

3 回答

• 4

  根据@Peter的说明，您需要使用客户端请求将数据 post 发送到服务器 .

  这是一个ASP.net页面，因此它需要您在回发时发送一些数据才能完成回调 .

  使用谷歌，我能够找到this作为概念证明 .

  以下是我在Linqpad中编写的片段，用于测试它 . 这里是：

  void Main()
  {
  
      WebClient webClient = new WebClient();
  
  
  
      byte[] b = webClient.DownloadData("http://www.mcxindia.com/sitepages/BhavCopyDateWise.aspx");
  
      string s = System.Text.Encoding.UTF8.GetString(b);
  
      var __EVENTVALIDATION = ExtractVariable(s, "__EVENTVALIDATION");
  
      __EVENTVALIDATION.Dump();
  
      var forms = new NameValueCollection(); 
  
      forms["__EVENTTARGET"] = "btnLink_Excel";
      forms["__EVENTARGUMENT"] = "";
      forms["__VIEWSTATE"] = ExtractVariable(s, "__VIEWSTATE");
      forms["mTbdate"] = "11%2F15%2F2011";
      forms["__EVENTVALIDATION"] = __EVENTVALIDATION;
  
  
      webClient.Headers.Set(HttpRequestHeader.ContentType, "application/x-www-form-urlencoded");
  
      var responseData = webClient.UploadValues(@"http://www.mcxindia.com/sitepages/BhavCopyDateWise.aspx", "POST", forms); 
      System.IO.File.WriteAllBytes(@"c:\11152011.csv", responseData);
  }
  
  private static string ExtractVariable(string s, string valueName)
  {
       string tokenStart = valueName + "\" value=\"";
       string tokenEnd = "\" />";
  
       int start = s.IndexOf(tokenStart) + tokenStart.Length;
       int length = s.IndexOf(tokenEnd, start) - start;
       return s.Substring(start, length);
  }
  

  回复于 2024-04-19T13:07:46+08:00
• 1

  using System.Net;
  
  WebClient webClient = new WebClient();
  webClient.DownloadFile("http://mysite.com/myfile.txt", @"c:\myfile.txt");
  

  但是如果文件太大，那么你应该使用异步方法 .
  检查此代码示例http://www.csharp-examples.net/download-files/

  回复于 2024-04-19T13:07:46+08:00
• 1

  使用WebClient有很多方法可以使用DownloadFile

  你必须先读这个http://msdn.microsoft.com/en-us/library/system.net.webclient.aspx

  如果您想要添加一些附加信息，可以使用WebClient.Headers，

  和使用

  using System.Net;
  
  WebClient webClient = new WebClient();
  var forms = new NameValueCollection();
  forms["token"] = "abc123";
  var responseData = webClient.UploadValues(@"http://blabla.com/download/?name=abc.exe", "POST", forms);
  System.IO.File.WriteAllBytes(@"D:\abc.exe");
  

  回复于 2024-04-19T13:07:46+08:00