How to download a file from a URL in C#?

问题:

What is a simple way of downloading a file from a URL path?

回答1:

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

回答2:

Include this namespace

using System.Net;

Download Asynchronously and put a ProgressBar to show the status of the download within the UI Thread Itself

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;
}

回答3:

Use 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())
{
    myStringWebResource = remoteUri + fileName;
    // Download the Web resource and save it into the current filesystem folder.
    myWebClient.DownloadFile(myStringWebResource, fileName);        
}

回答4:

using System.Net;

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

回答5:

Complete class to download a file while printing status to console.

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);
    }
}

Usage:

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

回答6:

Also you can use DownloadFileAsync method in WebClient class. It downloads to a local file the resource with the specified URI. Also this method does not block the calling thread.

Sample:

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

For more information:

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

回答7:

Check for a network connection using GetIsNetworkAvailable() to avoid creating empty files when not connected to a network.

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\");
    }                  
}

回答8:

Try using this:

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

回答9:

Below code contain logic for download file with original name

private string DownloadFile(string url)
    {

        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
        string filename = \"\";
        string destinationpath = Environment;
        if (!Directory.Exists(destinationpath))
        {
            Directory.CreateDirectory(destinationpath);
        }
        using (HttpWebResponse response = (HttpWebResponse)request.GetResponseAsync().Result)
        {
            string path = response.Headers[\"Content-Disposition\"];
            if (string.IsNullOrWhiteSpace(path))
            {
                var uri = new Uri(url);
                filename = Path.GetFileName(uri.LocalPath);
            }
            else
            {
                ContentDisposition contentDisposition = new ContentDisposition(path);
                filename = contentDisposition.FileName;

            }

            var responseStream = response.GetResponseStream();
            using (var fileStream = File.Create(System.IO.Path.Combine(destinationpath, filename)))
            {
                responseStream.CopyTo(fileStream);
            }
        }

        return Path.Combine(destinationpath, filename);
    }

回答10:

You may need to know the status and update a ProgressBar during the file download or use credentials before making the request.

Here it is, an example that covers these options. Lambda notation and String interpolation has been used:

using System.Net;
// ...

using (WebClient client = new WebClient()) {
    Uri ur = new Uri(\"http://remotehost.do/images/img.jpg\");

    //client.Credentials = new NetworkCredential(\"username\", \"password\");
    String credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(\"Username\" + \":\" + \"MyNewPassword\"));
    client.Headers[HttpRequestHeader.Authorization] = $\"Basic {credentials}\";

    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!\");
    };

    client.DownloadFileAsync(ur, @\"C:\\path\\newImage.jpg\");
}

回答11:

Instead of downloading this to a local file, you can convert to a byte stream object and store as a varbinary(MAX) BLOB in SQL Server.

Given that your table looks like:

CREATE TABLE [dbo].[Documents](
    [DocumentId] [int] IDENTITY(1,1) NOT NULL,
    [DocumentTypeId] [int] NOT NULL,
    [UploadedByMemberId] [int] NOT NULL,
    [DocumentTitle] [nvarchar](200) NOT NULL,
    [DocumentDescription] [nvarchar](2000) NULL,
    [FileName] [nvarchar](200) NOT NULL,
    [DateUploaded] [datetime] NOT NULL,
    [ApprovedForUsers] [bit] NOT NULL,
    [ApprovedByMemberId] [int] NOT NULL,
    [ApprovedDate] [datetime] NULL,
    [DocBLOB] [varbinary](max) NOT NULL,
 CONSTRAINT [PK_Documents] PRIMARY KEY CLUSTERED 
(
    [DocumentId] ASC
)

            SqlParameter Title = new SqlParameter(\"@Title\", SqlDbType.VarChar);
            SqlParameter FileName = new SqlParameter(\"@FileName\", SqlDbType.VarChar);
            SqlParameter DateFileUploaded = new SqlParameter(\"@DateUploaded\", SqlDbType.VarChar);
            SqlParameter DocBLOB = new SqlParameter(\"@DocBLOB\", SqlDbType.VarBinary);
            command.Parameters.Add(Title);
            command.Parameters.Add(FileName);
            command.Parameters.Add(DateFileUploaded);
            command.Parameters.Add(DocBLOB);
                        myStringWebResource = remoteUri + dataReader[\"FileName\"].ToString();
                        imgdownload = myWebClient.DownloadData(myStringWebResource);
                        querySQL = @\"INSERT INTO Documents(DocumentTypeId, UploadedByMemberId, DocumentTitle, DocumentDescription, FileName, DateUploaded, ApprovedForUsers, ApprovedByMemberId, ApprovedDate, DocBLOB) VALUES(1, 0, @Title, \'\', @FileName, @DateUploaded, 1, 0, GETDATE(), @DocBLOB);\";

                        Title.Value = dataReader[\"Title\"].ToString().Replace(\"\'\", \"\'\'\").Replace(\"\\\"\", \"\");
                        FileName.Value = dataReader[\"FileName\"].ToString().Replace(\"\'\", \"\'\'\").Replace(\"\\\"\", \"\");
                        DateFileUploaded.Value = dataReader[\"DateUploaded\"].ToString();
                        DocBLOB.Value = imgdownload;

                        command.CommandText = querySQL;
                        command.ExecuteNonQuery();