我试图下载一个客户端的数据到我的本地机器(编程),他们的web服务器非常非常慢,这导致我的WebClient对象超时。

这是我的代码:

WebClient webClient = new WebClient();

webClient.Encoding = Encoding.UTF8;
webClient.DownloadFile(downloadUrl, downloadFile);

有没有办法在这个对象上设置无限超时?如果不是,有没有人能帮我举个例子告诉我另一种方法?

该URL在浏览器中工作正常-只需要大约3分钟就能显示出来。


当前回答

在某些情况下,有必要在头文件中添加用户代理:

WebClient myWebClient = new WebClient();
myWebClient.DownloadFile(myStringWebResource, fileName);
myWebClient.Headers["User-Agent"] = "Mozilla/4.0 (Compatible; Windows NT 5.1; MSIE 6.0) (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

这就是我案子的解决办法。

信贷:

http://genjurosdojo.blogspot.com/2012/10/the-remote-server-returned-error-504.html

其他回答

不能让w.t otimeout代码在拔出网线时工作,它只是没有超时,移动到使用HttpWebRequest,现在做的工作。

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(downloadUrl);
request.Timeout = 10000;
request.ReadWriteTimeout = 10000;
var wresp = (HttpWebResponse)request.GetResponse();

using (Stream file = File.OpenWrite(downloadFile))
{
    wresp.GetResponseStream().CopyTo(file);
}

你需要使用HttpWebRequest而不是WebClient,因为你不能在WebClient上设置超时而不扩展它(即使它使用HttpWebRequest)。使用HttpWebRequest将允许你设置超时。

在某些情况下,有必要在头文件中添加用户代理:

WebClient myWebClient = new WebClient();
myWebClient.DownloadFile(myStringWebResource, fileName);
myWebClient.Headers["User-Agent"] = "Mozilla/4.0 (Compatible; Windows NT 5.1; MSIE 6.0) (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

这就是我案子的解决办法。

信贷:

http://genjurosdojo.blogspot.com/2012/10/the-remote-server-returned-error-504.html

为了完整起见,下面是kisp移植到VB的解决方案(不能向注释中添加代码)

Namespace Utils

''' <summary>
''' Subclass of WebClient to provide access to the timeout property
''' </summary>
Public Class WebClient
    Inherits System.Net.WebClient

    Private _TimeoutMS As Integer = 0

    Public Sub New()
        MyBase.New()
    End Sub
    Public Sub New(ByVal TimeoutMS As Integer)
        MyBase.New()
        _TimeoutMS = TimeoutMS
    End Sub
    ''' <summary>
    ''' Set the web call timeout in Milliseconds
    ''' </summary>
    ''' <value></value>
    Public WriteOnly Property setTimeout() As Integer
        Set(ByVal value As Integer)
            _TimeoutMS = value
        End Set
    End Property


    Protected Overrides Function GetWebRequest(ByVal address As System.Uri) As System.Net.WebRequest
        Dim w As System.Net.WebRequest = MyBase.GetWebRequest(address)
        If _TimeoutMS <> 0 Then
            w.Timeout = _TimeoutMS
        End If
        Return w
    End Function

End Class

End Namespace

用法:

using (var client = new TimeoutWebClient(TimeSpan.FromSeconds(10)))
{
    return await client.DownloadStringTaskAsync(url).ConfigureAwait(false);
}

类:

using System;
using System.Net;

namespace Utilities
{
    public class TimeoutWebClient : WebClient
    {
        public TimeSpan Timeout { get; set; }

        public TimeoutWebClient(TimeSpan timeout)
        {
            Timeout = timeout;
        }

        protected override WebRequest GetWebRequest(Uri uri)
        {
            var request = base.GetWebRequest(uri);
            if (request == null)
            {
                return null;
            }

            var timeoutInMilliseconds = (int) Timeout.TotalMilliseconds;

            request.Timeout = timeoutInMilliseconds;
            if (request is HttpWebRequest httpWebRequest)
            {
                httpWebRequest.ReadWriteTimeout = timeoutInMilliseconds;
            }

            return request;
        }
    }
}

但我推荐一个更现代的解决方案:

using System;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

public static async Task<string> ReadGetRequestDataAsync(Uri uri, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
{
    using var source = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
    if (timeout != null)
    {
        source.CancelAfter(timeout.Value);
    }

    using var client = new HttpClient();
    using var response = await client.GetAsync(uri, source.Token).ConfigureAwait(false);

    return await response.Content.ReadAsStringAsync().ConfigureAwait(false);
}

它将在超时后抛出OperationCanceledException异常。