如何從C＃網站下載文件？

Question

是否可以從Windows應用程序窗體中的網站下載文件並將其放入特定目錄？

Answer 1

隨着WebClient class：

using System.Net; 
//... 
WebClient Client = new WebClient(); 
Client.DownloadFile("http://i.stackoverflow.com/Content/Img/stackoverflow-logo-250.png", @"C:\folder\stackoverflowlogo.png"); 

Answer 2

使用WebClient.DownloadFile：

using (WebClient client = new WebClient()) 
{ 
    client.DownloadFile("http://csharpindepth.com/Reviews.aspx", 
         @"c:\Users\Jon\Test\foo.txt"); 
} 

Answer 3

當然，你只需要使用一個HttpWebRequest。

一旦你的HttpWebRequest設置，您可以響應流（根據MIME類型無論是BinaryWriter，或者TextWriter）保存到一個文件StreamWriter，你有你的硬盤驅動器上的文件。

編輯：忘了WebClient。除非您只需要使用GET來檢索您的文件，否則這種方式效果不錯。如果該網站要求您提供POST信息，則必須使用HttpWebRequest，所以我要離開我的答案。

Answer 4

試試這個例子：

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(); 
} 

的實現是在如下進行：

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

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

Answer 5

也可以在WebClient類中使用DownloadFileAsync方法。它將具有指定的URI的資源下載到本地文件。此方法也不會阻塞調用線程。

樣品：

webClient.DownloadFileAsync(new Uri("http://www.example.com/file/test.jpg"), "test.jpg"); 

欲瞭解更多信息：

http://csharpexamples.com/download-files-synchronous-asynchronous-url-c/

Answer 6

您可以使用此代碼從一個網站下載文件到桌面：

Answer 7

在發出請求之前，您可能需要知道文件下載期間的狀態或使用憑據。

下面是覆蓋這些選項的例子：

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"); 
} 

並實施了回調的功能如下：

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符號：用於處理事件

其他可能的選項

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!"); 
}); 

我們可以做的更好

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!"); 
}; 

或者

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!"); 
};