如何更改.NET WebClient对象的超时

您可以扩展超时:继承原始的WebClient类并重写WebRequest getter以设置自己的超时,如下例所示。

在我的例子中,MyWebClient是一个私有类:

private class MyWebClient : WebClient
{
    protected override WebRequest GetWebRequest(Uri uri)
    {
        WebRequest w = base.GetWebRequest(uri);
        w.Timeout = 20 * 60 * 1000;
        return w;
    }
}

你需要使用 HttpWebRequest 而不是 WebClient 因为你不能设置超时 网络客户端 不扩展它(即使它使用 HTTPWebRebug )使用 HTTPWebRebug 而是允许您设置超时。

第一个解决方案不适用于我,但这里有一些代码确实适用于我。

    private class WebClient : System.Net.WebClient
    {
        public int Timeout { get; set; }

        protected override WebRequest GetWebRequest(Uri uri)
        {
            WebRequest lWebRequest = base.GetWebRequest(uri);
            lWebRequest.Timeout = Timeout;
            ((HttpWebRequest)lWebRequest).ReadWriteTimeout = Timeout;
            return lWebRequest;
        }
    }

    private string GetRequest(string aURL)
    {
        using (var lWebClient = new WebClient())
        {
            lWebClient.Timeout = 600 * 60 * 1000;
            return lWebClient.DownloadString(aURL);
        }
    }

当拔出网线时,无法使w.timeout代码工作,它只是没有超时,移动到使用httpwebrequest并立即执行该任务。

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);
}

为了完整性,这里是kisp的解决方案移植到vb(不能在注释中添加代码)

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

如Sohnee所说,使用 System.Net.HttpWebRequest 并设置 Timeout 属性而不是使用 System.Net.WebClient .

但是,您不能设置无限超时值(不支持该值,尝试这样做会引发 ArgumentOutOfRangeException )

我建议先表演 HEAD HTTP 请求并检查 Content-Length 返回的头值确定要下载的文件中的字节数,然后相应地为后续文件设置超时值 GET 请求或只是指定一个非常长的超时值,您永远不会期望超过这个值。

'CORRECTED VERSION OF LAST FUNCTION IN VISUAL BASIC BY GLENNG

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  '<<< NOTICE: MyBase.GetWebRequest(address) DOES NOT WORK >>>
        End Function

用途:

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

班级:

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 timeoutInMillisecond = (int) Timeout.TotalMilliseconds;

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

            return request;
        }
    }
}