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
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
其他回答
你可以扩展超时:继承原始的WebClient类并重写webrequest getter来设置你自己的超时，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;
}
}
正如Sohnee所说，使用System.Net.HttpWebRequest并设置Timeout属性，而不是使用System.Net.WebClient。
然而，你不能设置一个无限的超时值(它不受支持，试图这样做会抛出一个argumentoutofranceexception)。
我建议首先执行HEAD HTTP请求，检查返回的Content-Length头值，以确定您正在下载的文件中的字节数，然后为后续的GET请求相应地设置超时值，或者简单地指定一个非常长的超时值，您不会期望超过这个超时值。
'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
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
根据kisp解决方案，这是我的编辑版本工作异步:
类WebConnection.cs
internal class WebConnection : WebClient
{
internal int Timeout { get; set; }
protected override WebRequest GetWebRequest(Uri Address)
{
WebRequest WebReq = base.GetWebRequest(Address);
WebReq.Timeout = Timeout * 1000 // Seconds
return WebReq;
}
}
异步任务
private async Task GetDataAsyncWithTimeout()
{
await Task.Run(() =>
{
using (WebConnection webClient = new WebConnection())
{
webClient.Timeout = 5; // Five seconds (the multiplication is in the override)
webClient.DownloadData("https://www.yourwebsite.com");
}
});
} // await GetDataAsyncWithTimeout()
否则，如果你不想使用async:
private void GetDataSyncWithTimeout()
{
using (WebConnection webClient = new WebConnection())
{
webClient.Timeout = 5; // Five seconds (the multiplication is in the override)
webClient.DownloadData("https://www.yourwebsite.com");
}
} // GetDataSyncWithTimeout()
