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
第一个解决方案不适合我，但这里有一些代码确实适合我。
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);
}
}
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()
'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
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。
对于任何需要WebClient超时工作的异步/任务方法的人，建议的解决方案将不起作用。以下是有效的方法:
public class WebClientWithTimeout : WebClient
{
//10 secs default
public int Timeout { get; set; } = 10000;
//for sync requests
protected override WebRequest GetWebRequest(Uri uri)
{
var w = base.GetWebRequest(uri);
w.Timeout = Timeout; //10 seconds timeout
return w;
}
//the above will not work for async requests :(
//let's create a workaround by hiding the method
//and creating our own version of DownloadStringTaskAsync
public new async Task<string> DownloadStringTaskAsync(Uri address)
{
var t = base.DownloadStringTaskAsync(address);
if(await Task.WhenAny(t, Task.Delay(Timeout)) != t) //time out!
{
CancelAsync();
}
return await t;
}
}
我在博客上写了完整的解决方法
