.net 为什么我的HttpClient.SendAsync被取消?
我正在使用为HttpClient创建的包装器类。当我调用SendAsync时,它抛出一个异常,声明“任务已取消” 我不明白为什么会发生这种情况,我没有向它传递取消令牌,而是使用wait在返回之前等待结果。有人能帮忙吗 编辑1:我已经了解到,如果编码不正确,HttpClient和在.NET 4.0中的使用存在问题。但是,我使用的是.NET4.5和wait关键字,所以我不应该有这个问题。此外,在抛出异常的断点期间,当我将鼠标悬停在HttpClient对象上时,并不表示该对象已被释放 发生异常的HttpClientWrapper类的代码段.net 为什么我的HttpClient.SendAsync被取消?,.net,vb.net,task-parallel-library,dotnet-httpclient,.net,Vb.net,Task Parallel Library,Dotnet Httpclient,我正在使用为HttpClient创建的包装器类。当我调用SendAsync时,它抛出一个异常,声明“任务已取消” 我不明白为什么会发生这种情况,我没有向它传递取消令牌,而是使用wait在返回之前等待结果。有人能帮忙吗 编辑1:我已经了解到,如果编码不正确,HttpClient和在.NET 4.0中的使用存在问题。但是,我使用的是.NET4.5和wait关键字,所以我不应该有这个问题。此外,在抛出异常的断点期间,当我将鼠标悬停在HttpClient对象上时,并不表示该对象已被释放 发生异常的Htt
Try
Return Await Client.SendAsync(Message, HttpCompletionOption.ResponseHeadersRead)
Catch ex As Exception
If DebugMode Then Output(OutputBufferKey, Method.ToString & " " & Url & " " & ex.Message, OutputType.Error)
End Try
自定义HttpClientWrapper类
Public Class HttpClientWrapper
Implements IDisposable
Protected Handler As New HttpClientHandler
Protected Client As HttpClient = Nothing
Public Property OutputBufferKey As String = Nothing
Public Property CancellationToken As CancellationToken? = Nothing
Public Sub New(Optional Proxy As WebProxy = Nothing, Optional Cookies As CookieContainer = Nothing, Optional UserAgent As String = Nothing, _
Optional OutputBufferKey As String = Nothing, Optional CancellationToken As CancellationToken? = Nothing)
Me.OutputBufferKey = OutputBufferKey
Me.CancellationToken = CancellationToken
If UserAgent Is Nothing Then UserAgent = RandomString(UserAgents)
SetCookies(Cookies)
SetProxy(Proxy)
Handler.AutomaticDecompression = DecompressionMethods.GZip Or DecompressionMethods.Deflate
Client = New HttpClient(Handler, True)
Client.Timeout = New TimeSpan(DefaultTimeout)
Client.DefaultRequestHeaders.Add("Accept-Encoding", "gzip, deflate")
Client.DefaultRequestHeaders.Add("Accept-Language", "en-US,en;q=0.5")
Client.DefaultRequestHeaders.Add("DNT", "1")
Client.DefaultRequestHeaders.Add("User-Agent", UserAgent)
End Sub
Public Sub New(User As User, Optional OutputBufferKey As String = Nothing, Optional CancellationToken As CancellationToken? = Nothing)
Me.New(User.GetProxy, User.Cookies, User.UserAgent, OutputBufferKey, CancellationToken)
End Sub
Public Sub New(User As User, Task As Task)
Me.New(User.GetProxy, User.Cookies, User.UserAgent, Task.OutputBufferKey, Task.CancellationToken.Token)
End Sub
Public Sub SetTimeout(Value As Integer)
Client.Timeout = New TimeSpan(Value)
End Sub
Private Sub SetCookies(Cookies As CookieContainer)
If Cookies Is Nothing Then
Handler.UseCookies = False
Else
Handler.UseCookies = True
Handler.CookieContainer = Cookies
End If
End Sub
Private Sub SetProxy(Proxy As WebProxy)
If Proxy Is Nothing Then
Handler.UseProxy = False
Else
Handler.UseProxy = True
Handler.Proxy = Proxy
End If
End Sub
Public Async Function WebRequestByteAsync(Url As String, Optional RequestMethod As RequestMethod = RequestMethod.GET, Optional Content As Object = Nothing, _
Optional ContentType As ContentType = ContentType.Default, Optional Accept As String = DefaultAcceptString, _
Optional AdditionalHeaders As NameValueCollection = Nothing, Optional Referer As String = Nothing, Optional NoCache As Boolean = False) _
As Tasks.Task(Of Byte())
Using Response As HttpResponseMessage = Await WebRequestAsync(Url, RequestMethod, Content, ContentType, Accept, AdditionalHeaders, Referer, NoCache)
If Response IsNot Nothing Then
If Response.StatusCode = HttpStatusCode.OK Then
Return Await GetResponseByteAsync(Response)
Else
Output(OutputBufferKey, Url & " did not return OK (200)", OutputType.Error)
End If
End If
Return Nothing
End Using
End Function
Public Async Function WebRequestStringAsync(Url As String, Optional RequestMethod As RequestMethod = RequestMethod.GET, Optional Content As Object = Nothing, _
Optional ContentType As ContentType = ContentType.Default, Optional Accept As String = DefaultAcceptString, _
Optional AdditionalHeaders As NameValueCollection = Nothing, Optional Referer As String = Nothing, Optional NoCache As Boolean = False) _
As Tasks.Task(Of String)
Using Response As HttpResponseMessage = Await WebRequestAsync(Url, RequestMethod, Content, ContentType, Accept, AdditionalHeaders, Referer, NoCache)
If Response IsNot Nothing Then
If Response.StatusCode = HttpStatusCode.OK Then
Return Await GetResponseStringAsync(Response)
Else
Output(OutputBufferKey, Url & " did not return OK (200)", OutputType.Error)
End If
End If
Return Nothing
End Using
End Function
Public Async Function WebRequestAsync(Url As String, Optional RequestMethod As RequestMethod = RequestMethod.GET, Optional Content As Object = Nothing, _
Optional ContentType As ContentType = ContentType.Default, Optional Accept As String = DefaultAcceptString, _
Optional AdditionalHeaders As NameValueCollection = Nothing, Optional Referer As String = Nothing, Optional NoCache As Boolean = False, _
Optional CanBeCancelled As Boolean = True) _
As Tasks.Task(Of HttpResponseMessage)
Dim Method As HttpMethod = Nothing
Select Case RequestMethod
Case Variables.RequestMethod.DELETE : Method = HttpMethod.Delete
Case Variables.RequestMethod.GET : Method = HttpMethod.Get
Case Variables.RequestMethod.OPTIONS : Method = HttpMethod.Options
Case Variables.RequestMethod.POST : Method = HttpMethod.Post
Case Variables.RequestMethod.PUT : Method = HttpMethod.Put
End Select
'prepare message
Dim Message As New HttpRequestMessage(Method, Url)
Message.Headers.ExpectContinue = False
Message.Headers.TryAddWithoutValidation("Accept", Accept)
If Referer IsNot Nothing Then Message.Headers.Add("Referer", Referer)
If NoCache Then
Message.Headers.Add("Pragma", "no-cache")
Message.Headers.Add("Cache-Control", "no-cache")
End If
If AdditionalHeaders IsNot Nothing Then
For Each Key In AdditionalHeaders.AllKeys
Message.Headers.TryAddWithoutValidation(Key, AdditionalHeaders(Key))
Next
End If
'set content
If Content IsNot Nothing Then
Dim ContentTypeString As String = GetEnumDescription(ContentType)
Dim ContentBytes As Byte() = Nothing
If TypeOf Content Is String Then
ContentBytes = Encoding.UTF8.GetBytes(CType(Content, String))
ElseIf TypeOf Content Is Byte() Then
ContentBytes = CType(Content, Byte())
ElseIf TypeOf Content Is MultiPartPostData Then
Dim MultiPartPostData As MultiPartPostData = CType(Content, MultiPartPostData)
ContentBytes = MultiPartPostData.Bytes
ContentTypeString += "; boundary=" & MultiPartPostData.Boundary
End If
Dim ByteArrayContent As New ByteArrayContent(ContentBytes)
ByteArrayContent.Headers.Add("Content-Type", ContentTypeString)
Message.Content = ByteArrayContent
End If
'get response
Output(OutputBufferKey, RequestMethod.ToString & " " & Url, OutputType.Debug)
Try
Return Await Client.SendAsync(Message, HttpCompletionOption.ResponseHeadersRead)
Catch ex As Exception
If DebugMode Then Output(OutputBufferKey, Method.ToString & " " & Url & " " & ex.Message, OutputType.Error)
End Try
Return Nothing
End Function
Public Async Function GetResponseByteAsync(Response As HttpResponseMessage) As Tasks.Task(Of Byte())
If Response Is Nothing Then
If DebugMode Then Output(OutputBufferKey, "Unable read content from response message: Is nothing", OutputType.Error)
Else
Try
Return Await Response.Content.ReadAsByteArrayAsync
Catch ex As Exception
If DebugMode Then Output(OutputBufferKey, "Unable read content from " & Response.RequestMessage.RequestUri.ToString & ": " & ex.Message, OutputType.Error)
End Try
End If
Return Nothing
End Function
Public Async Function GetResponseStringAsync(Response As HttpResponseMessage) As Tasks.Task(Of String)
If Response Is Nothing Then
If DebugMode Then Output(OutputBufferKey, "Unable read content from response message: Is nothing", OutputType.Error)
Else
Try
Return Await Response.Content.ReadAsStringAsync
Catch ex As Exception
If DebugMode Then Output(OutputBufferKey, "Unable read content from " & Response.RequestMessage.RequestUri.ToString & ": " & ex.Message, OutputType.Error)
End Try
End If
Return Nothing
End Function
#Region "IDisposable Support"
Private disposedValue As Boolean ' To detect redundant calls
' IDisposable
Protected Overridable Sub Dispose(disposing As Boolean)
If Not Me.disposedValue Then
If disposing Then
If Client IsNot Nothing Then Client.Dispose()
End If
End If
Me.disposedValue = True
End Sub
' This code added by Visual Basic to correctly implement the disposable pattern.
Public Sub Dispose() Implements IDisposable.Dispose
' Do not change this code. Put cleanup code in Dispose(disposing As Boolean) above.
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
#End Region
End Class
主代码
Module Main
Dim ProxyUrl As String = "proxies.txt"
Sub main()
DebugMode = True
OutputToConsole = True
Dim Proxies As New ProxyList(ProxyUrl)
Try
Run(Proxies).GetAwaiter.GetResult()
Catch ex As Exception
MsgBox(ex.Message)
End Try
Console.ReadLine()
End Sub
Public Async Function Run(Proxies As ProxyList) As Tasks.Task
Dim Proxy As WebProxy = Await Proxies.GetProxy
Using Client As New HttpClientWrapper(Proxy)
Dim Response As String = Await Client.WebRequestStringAsync("http://www.google.com")
If Response IsNot Nothing Then Console.WriteLine(Response)
End Using
End Function
End Module
HTTPClient
表示任务在达到超时时已取消:您确定有足够大的超时/web服务及时响应吗?HTTPClient
表示任务在达到超时时已取消:您确定有足够大的超时/web服务及时响应吗时尚?感谢您为我指明了正确的方向,我正在使用新的TimeSpan(滴答声)设置超时,滴答声为8000。我把滴答声误认为是毫秒。问题解决了,酷!对于未来来说,这是一个好主意——如果你能在问题中加入例外,这将是一个更好的问题。感谢你的建议,但不确定你的意思。有没有一种简单的方法可以获取异常的所有详细信息以放入问题中?只需将except.ToString()输出复制到问题中,并将其格式化为code/quoteThanks,以便为我指明正确的方向。我正在使用新的TimeSpan(Ticks)设置超时,Ticks为8000。我把滴答声误认为是毫秒。问题解决了,酷!对于未来来说,这是一个好主意——如果你能在问题中加入例外,这将是一个更好的问题。感谢你的建议,但不确定你的意思。有没有一种简单的方法可以将异常的所有详细信息都放到问题中?只需将except.ToString()输出复制到问题中,并将其格式化为code/quote即可