如何将异步HTTPWEBREQUEST和一些回调功能联系起来?vb.net

Question

对于获取数据异步，我在公共VB模块中编写了异步HTTPWebrequest函数，然后以三种以上的形式写了一个Get html函数。

在模块中：

Private Sub GetRequestStreamCallback(ByVal asynchronousResult As IAsyncResult) 
    Dim request As HttpWebRequest = CType(asynchronousResult.AsyncState, HttpWebRequest)
    Dim postStream As Stream = request.EndGetRequestStream(asynchronousResult)
    Dim postData As String = <<<<<POST STRING DATA HERE>>>>>
    Dim byteArray As Byte() = System.Text.Encoding.UTF8.GetBytes(postData)
    postStream.Write(byteArray, 0, postData.Length)
    postStream.Close()
    Dim result As IAsyncResult = CType(request.BeginGetResponse(AddressOf GetResponseCallback, request),  _
        IAsyncResult)
End Sub
Private Sub GetResponseCallback(ByVal asynchronousResult As IAsyncResult) 
    Dim request As HttpWebRequest = CType(asynchronousResult.AsyncState, HttpWebRequest)
    Dim response As HttpWebResponse = CType(request.EndGetResponse(asynchronousResult), HttpWebResponse)
    Dim streamResponse As Stream = response.GetResponseStream()
    Dim streamRead As New StreamReader(streamResponse)
    Dim responseString As String = streamRead.ReadToEnd()
    <<<<RETURING THE RECEIVED DATA TO THE FORM WHICH CALLED GETTING HTML FUNC.>>>>
    streamResponse.Close()
    streamRead.Close()
    response.Close()
End Sub
Public Sub GetHTMLAsync(ByVal POSTDATA as String,  <<<<FUNCTION ADDRESS OR SUCH THING TO CALL WHEN THE ASYNC PROCEDURE IS DONE>>>>)
    Req = CType(WebRequest.Create("http://hi.asdf.com/getinformation.php"), HttpWebRequest)
    Req.Method = "POST"
    Req.ContentType = "application/x-www-form-urlencoded; charset=utf-8"
    Req.CookieContainer = CookieC
    Req.Timeout = 1000 * 30
    <DO SOMETHING TO DELIVER [POSTDATA] AND ["FUNCTION" ARGUMENT] TO ASYNC PROCEDURE ABOVE>
    'Async
    Dim result As IAsyncResult = CType(Req.BeginGetRequestStream(AddressOf GetRequestStreamCallback, Req), IAsyncResult)
End Sub

形式：

Private Sub btnGet_Click(sender As Object, e As EventArgs) Handles btnGet.Click
  GetHTMLAsync("name=klados&data=birthday", <<<getDataDoneCallBack something..>>>)
End Sub

Public Sub getDataDoneCallBack(ByVal text as String)
  'Show the received data(string)
  Msgbox(text)
End Sub

因此，当我调用Gethtmlasync时，它将帖子字符串移交给模块中的异步WebRequest函数，当接收到响应数据完成时，它将以表单调用回调函数。

在这里，我只想知道1.如何将帖子字符串移交给getRequestStreamCallback函数？2.如何从模块中的getResponsecallback以特定形式回电？

因为btnget（调用" gethtmlasync"函数）按钮以几种形式存在，而不是单个形式，所以后数据和回电函数不应纠结或跨越。

我真的很感谢答案。祝你有美好的一天！

摘要中的问题

我的问题很简单。使用.NET Framework 3.5（无等待功能），我想制作两个或多个函数（subs），其中包含独立的async httpwebrequests以一种form.vb（或模块，class）。谢谢！

呼叫gethtml（地址，参数，callback_function）

=>获取来自参数的地址的信息

=>如果获得数据，它将调用callback_function

呼叫gethtml可以同时

gethtml（" http://a.com"，" name = hi"，function1）

gethtml（" http://b.com"，" day = happy"，function2）

应该单独和独立地工作，不应将接收数据合并。

如果这有些困难，具有相同形式的不同回调功能的不同GetHtml功能也可以！

gethtml_a（" a.com"，...）=>回电gothtml_a

gethtml_b（" b.com"，...）=>回电gothtml_b

以相同的形式.vb或module.vb也很棒！

Answer 1

这听起来像是单独的背景工作者的好用途。每个背景工作者都使用自己的线程来执行独立于彼此的任务。您可以使用RunWorkerCompleted事件完成后台工作人员后传递数据。

Answer 2

如果使用lambda表达式而不是用于回调的普通函数，那么您的代码将变得更加简单。这样，您将"捕获"您需要传递的状态。这是您的代码外观的简化示例（vb.net对我来说不是一种熟悉的语言，因此，如果有语法问题，则很抱歉）：

Public Sub GetHTMLAsync(ByVal postData as String, callback as Action(Of String))
    'Req = ...
    Req.BeginGetRequestStream( _
        Sub (asynchronousResult1)
            Dim postStream As Stream = Req.EndGetRequestStream(asynchronousResult1)
            Dim byteArray As Byte() = System.Text.Encoding.UTF8.GetBytes(postData)
            postStream.Write(byteArray, 0, byteArray.Length)
            '...
            Req.BeginGetResponse( _
                Sub (asynchronousResult2)
                    Dim response As HttpWebResponse = Req.EndGetResponse(asynchronousResult2)
                    Dim streamResponse As Stream = response.GetResponseStream()
                    Dim streamRead As New StreamReader(streamResponse)
                    Dim responseString As String = streamRead.ReadToEnd()
                    callback(responseString)
                    '...
                End Sub, Req)
        End Sub, Req)    
End Sub

请注意，如何通过像这样定义Sub 内联，我可以访问其范围之外的变量。这称为封闭。因此，BeginGetRequestStream的回调能够"查看" postData，BeginGetResponse的回调能够"查看" callback，因此可以调用。