66

是否可以从 Windows 应用程序表单中的网站下载文件并将其放入某个目录？

4

7 回答 7

117

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");
于 2009-02-08T07:56:59.583 回答
85

使用WebClient.DownloadFile：

using (WebClient client = new WebClient())
{
    client.DownloadFile("http://csharpindepth.com/Reviews.aspx", 
                        @"c:\Users\Jon\Test\foo.txt");
}
于 2009-02-08T07:54:27.513 回答
19

在发出请求之前，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示例：

Uri ur = new Uri("http://remotehost.do/images/img.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");
}

回调函数实现如下：

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!");
}

(Ver 2) - Lambda 表示法：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!");
});

(Ver 3) - 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!");
};

（版本 4）- 或

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!");
};
于 2016-01-19T14:27:55.810 回答
13

当然，您只需使用HttpWebRequest.

HttpWebRequest设置完成后，您可以将响应流保存到一个文件（StreamWriter取决于mimetypeBinaryWriter或 a ），并且您的硬盘驱动器上有一个文件。TextWriter

编辑：忘记了WebClient。除非您只需要使用GET来检索文件，否则效果很好。如果该站点要求您向其POST提供信息，则您必须使用 a HttpWebRequest，因此我将保留我的答案。

于 2009-02-08T07:54:53.627 回答
2

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");
于 2014-10-07T09:29:56.873 回答
0

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();
}

实现如下：

TheDownload("@"c:\Temporal\Test.txt"");

来源：http ://www.systemdeveloper.info/2014/03/force-downloading-file-from-c.html

于 2014-03-16T17:28:20.907 回答
0

您也可以在课堂上使用DownloadFileAsync方法。WebClient它将具有指定的资源下载到本地文件URI。此方法也不会阻塞调用线程。

样本：

    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/

于 2014-06-16T06:05:47.387 回答