如何从C#中的URL下载文件？

从URL路径下载文件的简单方法是什么？

1> Raj Kumar..：

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using (var client = new WebClient())
{
    client.DownloadFile("http://example.com/file/song/a.mpeg", "a.mpeg");
}

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有史以来最好的解决方案,但我想添加一条重要的行'client.Credentials = new NetworkCredential("UserName","Password");'

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一个受欢迎的副作用:此方法还支持本地文件作为第一个参数

2> Sayka..：

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包括此命名空间

using System.Net;

异步下载并放入ProgressBar以在UI线程本身中显示下载的状态

private void BtnDownload_Click(object sender, RoutedEventArgs e)
{
    using (WebClient wc = new WebClient())
    {
        wc.DownloadProgressChanged += wc_DownloadProgressChanged;
        wc.DownloadFileAsync (
            // Param1 = Link of file
            new System.Uri("http://www.sayka.com/downloads/front_view.jpg"),
            // Param2 = Path to save
            "D:\\Images\\front_view.jpg"
        );
    }
}
// Event to track the progress
void wc_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
    progressBar.Value = e.ProgressPercentage;
}

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大多数人在下载时都更喜欢进度条.所以我写了最简单的方法来做到这一点.这可能不是答案,但它符合Stackoverflow的要求.那是为了帮助别人.

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问题要求最简单的方法.制作更复杂并不是最简单的.

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如果您忽略进度条,这就像其他答案一样简单.此答案还包括命名空间并使用I/O的异步.此问题并不是要求最简单的方法,只是一种简单的方法.:)

3> vbroto..：

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用途System.Net.WebClient.DownloadFile:

string remoteUri = "http://www.contoso.com/library/homepage/images/";
string fileName = "ms-banner.gif", myStringWebResource = null;

// Create a new WebClient instance.
using (WebClient myWebClient = new WebClient())
{
    string myStringWebResource = remoteUri + fileName;
    // Download the Web resource and save it into the current filesystem folder.
    myWebClient.DownloadFile(myStringWebResource, fileName);        
}

4> 小智..：

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using System.Net;

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

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欢迎来到SO!通常,对已经有很高评价答案的现有和旧问题发布低质量答案并不是一个好主意.

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我从seanb的评论中找到了答案,但我真的更喜欢这种"低质量"的答案.它完整​​(使用声明),简洁易懂.作为一个老问题是无关紧要的,恕我直言.

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但它认为使用Using的答案要好得多,因为我认为WebClient应该在使用后处理掉.将其放入使用中可确保其处理.

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它与此代码示例中的disposes无关......这里的using语句只显示要使用的命名空间,而不是WebClient用于处理...

5> Jonas_Hess..：

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在将状态打印到控制台时完成下载文件的类.

using System;
using System.ComponentModel;
using System.IO;
using System.Net;
using System.Threading;

class FileDownloader
{
    private readonly string _url;
    private readonly string _fullPathWhereToSave;
    private bool _result = false;
    private readonly SemaphoreSlim _semaphore = new SemaphoreSlim(0);

    public FileDownloader(string url, string fullPathWhereToSave)
    {
        if (string.IsNullOrEmpty(url)) throw new ArgumentNullException("url");
        if (string.IsNullOrEmpty(fullPathWhereToSave)) throw new ArgumentNullException("fullPathWhereToSave");

        this._url = url;
        this._fullPathWhereToSave = fullPathWhereToSave;
    }

    public bool StartDownload(int timeout)
    {
        try
        {
            System.IO.Directory.CreateDirectory(Path.GetDirectoryName(_fullPathWhereToSave));

            if (File.Exists(_fullPathWhereToSave))
            {
                File.Delete(_fullPathWhereToSave);
            }
            using (WebClient client = new WebClient())
            {
                var ur = new Uri(_url);
                // client.Credentials = new NetworkCredential("username", "password");
                client.DownloadProgressChanged += WebClientDownloadProgressChanged;
                client.DownloadFileCompleted += WebClientDownloadCompleted;
                Console.WriteLine(@"Downloading file:");
                client.DownloadFileAsync(ur, _fullPathWhereToSave);
                _semaphore.Wait(timeout);
                return _result && File.Exists(_fullPathWhereToSave);
            }
        }
        catch (Exception e)
        {
            Console.WriteLine("Was not able to download file!");
            Console.Write(e);
            return false;
        }
        finally
        {
            this._semaphore.Dispose();
        }
    }

    private void WebClientDownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
        Console.Write("\r     -->    {0}%.", e.ProgressPercentage);
    }

    private void WebClientDownloadCompleted(object sender, AsyncCompletedEventArgs args)
    {
        _result = !args.Cancelled;
        if (!_result)
        {
            Console.Write(args.Error.ToString());
        }
        Console.WriteLine(Environment.NewLine + "Download finished!");
        _semaphore.Release();
    }

    public static bool DownloadFile(string url, string fullPathWhereToSave, int timeoutInMilliSec)
    {
        return new FileDownloader(url, fullPathWhereToSave).StartDownload(timeoutInMilliSec);
    }
}

用法:

static void Main(string[] args)
{
    var success = FileDownloader.DownloadFile(fileUrl, fullPathWhereToSave, timeoutInMilliSec);
    Console.WriteLine("Done  - success: " + success);
    Console.ReadLine();
}

6> 小智..：

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您也可以在WebClient类中使用DownloadFileAsync方法.它将具有指定URI的资源下载到本地文件.此方法也不会阻止调用线程.

样品:

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

欲获得更多信息:

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

7> 小智..：

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试试这个:

private void downloadFile(string url)
{
     string file = System.IO.Path.GetFileName(url);
     WebClient cln = new WebClient();
     cln.DownloadFile(url, file);
}

8> 小智..：

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检查网络连接,GetIsNetworkAvailable()以避免在未连接到网络时创建空文件.

if (System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable())
{
    using (System.Net.WebClient client = new System.Net.WebClient())
    {                        
          client.DownloadFileAsync(new Uri("http://www.examplesite.com/test.txt"),
          "D:\\test.txt");
    }                  
}