Multithreading + asynchronous posting xml (threadpool)

[pixie213]

Hi i have been struggling with this for a few days now. I am attempting to send an xml string to a http address multiple times and receive an xml response from the site. I have so far managed to construct the following module that handles the asynchronous post.

      Imports System.Net

      Imports System.IO

      Imports System.Threading

      Imports System.Collections

      Module Module1

      Public Class RequestState

      Public Request As HttpWebRequest

      Public URL As String

      Public Sub New()

      Request = Nothing

      End Sub

      End Class

       

      Public Sub CreateAsyncWebRequest(ByVal MyURL As String, ByVal XMLInputString As String)

      Dim oHttp As HttpWebRequest = DirectCast(WebRequest.Create(MyURL), HttpWebRequest)

      oHttp.Method = "POST"

      Dim postBuffer As Byte() = System.Text.Encoding.ASCII.GetBytes(XMLInputString)

      oHttp.ContentLength = postBuffer.Length

      Dim postData As Stream = oHttp.GetRequestStream()

      postData.Write(postBuffer, 0, postBuffer.Length)

      postData.Close()

      Dim objState As New RequestState

      objState.Request = oHttp

      objState.URL = MyURL

      Dim result As IAsyncResult = DirectCast(oHttp.BeginGetResponse(New AsyncCallback(AddressOf ProcessAsyncWebResponse), objState), IAsyncResult)

      ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, _

      New WaitOrTimerCallback(AddressOf ScanTimeoutCallback), _

      objState, (30 * 1000), True)

      End Sub

      Private Sub ScanTimeoutCallback(ByVal Request As Object, ByVal TimedOut As Boolean)

      If TimedOut Then

      Dim objState As RequestState = DirectCast(Request, RequestState)
 
      If Not (Request Is Nothing) Then

      objState.Request.Abort()

      Console.WriteLine(objState.URL + " is processed")

      End If

      End If

      End Sub

       

      Private Sub ProcessAsyncWebResponse(ByVal Result As IAsyncResult)

      Dim objState As RequestState = DirectCast(Result.AsyncState, RequestState)

      Dim oHttp As HttpWebRequest = DirectCast(objState.Request, HttpWebRequest)

      Dim myResponse As HttpWebResponse

      Dim loResponseStream As StreamReader

      Dim strxmlout As String

      Try

      myResponse = DirectCast(oHttp.EndGetResponse(Result), HttpWebResponse)

      loResponseStream = New StreamReader(myResponse.GetResponseStream(), System.Text.Encoding.ASCII)

      strxmlout = loResponseStream.ReadToEnd()

      'rtbSendNotes.Text = m_xmlOut

      'frmMainProcess.TextBox2.Text += strxmlout

      writelog.writelogfile(objState.URL + " is processed-i win -------" + strxmlout)

      Catch ex As Exception

      'Exception handling code

      writelog.writelogfile(objState.URL + " is processed with exception: " + ex.Message)

      Finally

      If Not (myResponse Is Nothing) Then

      myResponse.Close()

      End If

      If Not (loResponseStream Is Nothing) Then

      loResponseStream.Close()

      End If

      End Try

      frmMainProcess.TextBox2.Refresh()

      End Sub

       

      End Module

called by the following procedure

CreateAsyncWebRequest(My.Settings.MPIURL, strxmlreq)

So for testing i am
1 - clicking a button which is firing the above procedure.
2 - sending the xml using the async post
3 - receiving an xml string
4 - appending the string to a txt file.

Now i would have thought i could hit the button a few 100 times and these would be qued into nthe threadpool and the responses handled as they are returned. However as soon as i click the button the UI freezes and is non responsive until the complete process has completed.

One way to get around this is to use multiple background workers to run the procedure but i would be looking to run about 25 + of them and i dont see the point as i am already using threadpool.

can anyone suggest how to resolve this problem.

Thanks in advance.

 

[JohnH]

HttpWebRequest.GetRequestStream Method (System.Net)

Your application cannot mix synchronous and asynchronous methods for a particular request. If you call the GetRequestStream method, you must use the GetResponse method to retrieve the response.