如何从C＃网站下载文件
是否可以从Windows应用程序窗体中的网站下载文件并将其放入特定目录？
使用WebClient类 ：
using System.Net; //... WebClient Client = new WebClient (); Client.DownloadFile("http://i.stackoverflow.com/Content/Img/stackoverflow-logo-250.png", @"C:\folder\stackoverflowlogo.png"); 使用WebClient.DownloadFile ：
using (WebClient client = new WebClient()) { client.DownloadFile("http://csharpindepth.com/Reviews.aspx", @"c:\Users\Jon\Test\foo.txt"); }
当然，你只是使用HttpWebRequest 。
设置HttpWebRequest后，可以将响应stream保存到文件StreamWriter （ BinaryWriter或TextWriter取决于mimetype），并在硬盘上有一个文件。
编辑：忘记WebClient 。 这很好，除非你只需要使用GET来检索你的文件。 如果网站要求你发布信息，你将不得不使用HttpWebRequest ，所以我要离开我的答案了。
在提出请求之前，您可能需要知道文件下载期间的状态或使用凭据。
这是一个涵盖这些选项的例子：
Uri ur = new Uri("http://remotehost.dohttp://img.dovov.comimg.jpg"); using (WebClient client = new WebClient()) { //client.Credentials = new NetworkCredential("username", "password"); String credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes("Username" + ":" + "MyNewPassword")); client.Headers[HttpRequestHeader.Authorization] = $"Basic {credentials}"; client.DownloadProgressChanged += WebClientDownloadProgressChanged; client.DownloadDataCompleted += WebClientDownloadCompleted; client.DownloadFileAsync(ur, @"C:\path\newImage.jpg"); }
而callback的function实现如下：
void WebClientDownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e) { Console.WriteLine("Download status: {0}%.", e.ProgressPercentage); // updating the UI Dispatcher.Invoke(() => { progressBar.Value = e.ProgressPercentage; }); } void WebClientDownloadCompleted(object sender, DownloadDataCompletedEventArgs e) { Console.WriteLine("Download finished!"); }
Lambda符号：处理事件的其他可能选项
client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(delegate(object sender, DownloadProgressChangedEventArgs e) { Console.WriteLine("Download status: {0}%.", e.ProgressPercentage); // updating the UI Dispatcher.Invoke(() => { progressBar.Value = e.ProgressPercentage; }); }); client.DownloadDataCompleted += new DownloadDataCompletedEventHandler(delegate(object sender, DownloadDataCompletedEventArgs e){ Console.WriteLine("Download finished!"); });
我们可以做得更好
client.DownloadProgressChanged += (object sender, DownloadProgressChangedEventArgs e) => { Console.WriteLine("Download status: {0}%.", e.ProgressPercentage); // updating the UI Dispatcher.Invoke(() => { progressBar.Value = e.ProgressPercentage; }); }; client.DownloadDataCompleted += (object sender, DownloadDataCompletedEventArgs e) => { Console.WriteLine("Download finished!"); };
要么
client.DownloadProgressChanged += (o, e) => { Console.WriteLine($"Download status: {e.ProgressPercentage}%."); // updating the UI Dispatcher.Invoke(() => { progressBar.Value = e.ProgressPercentage; }); }; client.DownloadDataCompleted += (o, e) => { Console.WriteLine("Download finished!"); };
您可以使用此代码将文件从网站下载到桌面：
using System.Net; WebClient Client = new WebClient (); client.DownloadFileAsync(new Uri("http://www.Address.com/File.zip"), Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + "File.zip");
试试这个例子：
public void TheDownload(string path) { System.IO.FileInfo toDownload = new System.IO.FileInfo(HttpContext.Current.Server.MapPath(path)); HttpContext.Current.Response.Clear(); HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + toDownload.Name); HttpContext.Current.Response.AddHeader("Content-Length", toDownload.Length.ToString()); HttpContext.Current.Response.ContentType = "application/octet-stream"; HttpContext.Current.Response.WriteFile(patch); HttpContext.Current.Response.End(); }
实现过程如下：
TheDownload("@"c:\Temporal\Test.txt"");
来源： http : //www.systemdeveloper.info/2014/03/force-downloading-file-from-c.html
您也可以在WebClient类中使用DownloadFileAsync方法。 它使用指定的URI将资源下载到本地文件。 此方法也不会阻塞调用线程。
样品：
webClient.DownloadFileAsync(new Uri("http://www.example.com/file/test.jpg"), "test.jpg");
了解更多信息：
http://csharpexamples.com/download-files-synchronous-asynchronous-url-c/
