Untitled

Imports System
Imports System.Net
Imports System.IO
Imports System.Text
Imports System.Threading
Imports Microsoft.VisualBasic


Public Class RequestState
    ' This class stores the state of the request
    Private Shared BUFFER_SIZE As Integer = 1024
    Public requestData As StringBuilder
    Public bufferRead() As Byte
    Public request As WebRequest
    Public response As WebResponse
    Public responseStream As Stream

    Public Sub New()
        bufferRead = New Byte(BUFFER_SIZE) {}
        requestData = New StringBuilder("")
        request = Nothing
        responseStream = Nothing
    End Sub ' New
End Class ' RequestState

Class WebRequest_BeginGetResponse
    Public Shared allDone As New ManualResetEvent(False)
    Private Shared BUFFER_SIZE As Integer = 1024

    Shared Sub Main()
        Try
            ' Create a new webrequest to the mentioned URL.
            Dim myWebRequest As WebRequest = WebRequest.Create("http://www.contoso.com")
            ' Create a new instance of the RequestState.
            Dim myRequestState As New RequestState()
            ' The 'WebRequest' object is associated to the 'RequestState' object.
            myRequestState.request = myWebRequest
            ' Start the Asynchronous call for response.
            Dim asyncResult As IAsyncResult = CType(myWebRequest.BeginGetResponse(AddressOf RespCallback, myRequestState), IAsyncResult)
            allDone.WaitOne()
            ' Release the WebResponse resource.
            myRequestState.response.Close()
            Console.Read()
        Catch e As WebException
            Console.WriteLine("WebException raised!")
            Console.WriteLine(ControlChars.Cr + "{0}", e.Message)
            Console.WriteLine(ControlChars.Cr + "{0}", e.Status)
        Catch e As Exception
            Console.WriteLine("Exception raised!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
        End Try
    End Sub ' Main

    Private Shared Sub RespCallback(ByVal asynchronousResult As IAsyncResult)
        Try
            ' Set the State of request to asynchronous.
            Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
            Dim myWebRequest1 As WebRequest = myRequestState.request
            ' End the Asynchronous response.
            myRequestState.response = myWebRequest1.EndGetResponse(asynchronousResult)
            ' Read the response into a 'Stream' object.
            Dim responseStream As Stream = myRequestState.response.GetResponseStream()
            myRequestState.responseStream = responseStream
            ' Begin the reading of the contents of the HTML page and print it to the console.
            Dim asynchronousResultRead As IAsyncResult = responseStream.BeginRead(myRequestState.bufferRead, 0, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
        Catch e As WebException
            Console.WriteLine("WebException raised!")
            Console.WriteLine(ControlChars.Cr + "{0}", e.Message)
            Console.WriteLine(ControlChars.Cr + "{0}", e.Status)
        Catch e As Exception
            Console.WriteLine("Exception raised!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
        End Try
    End Sub ' RespCallback
    Private Shared Sub ReadCallBack(ByVal asyncResult As IAsyncResult)
        Try
            ' Result state is set to AsyncState.
            Dim myRequestState As RequestState = CType(asyncResult.AsyncState, RequestState)
            Dim responseStream As Stream = myRequestState.responseStream
            Dim read As Integer = responseStream.EndRead(asyncResult)
            ' Read the contents of the HTML page and then print to the console.
            If read > 0 Then
                myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.bufferRead, 0, read))
                Dim asynchronousResult As IAsyncResult = responseStream.BeginRead(myRequestState.bufferRead, 0, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
            Else
                Console.WriteLine(ControlChars.Cr + "The HTML page Contents are:  ")
                If myRequestState.requestData.Length > 1 Then
                    Dim sringContent As String
                    sringContent = myRequestState.requestData.ToString()
                    Console.WriteLine(sringContent)
                End If
                Console.WriteLine(ControlChars.Cr + "Press 'Enter' key to continue........")
                responseStream.Close()
                allDone.Set()
            End If
        Catch e As WebException
            Console.WriteLine("WebException raised!")
            Console.WriteLine(ControlChars.Cr + "{0}", e.Message)
            Console.WriteLine(ControlChars.Cr + "{0}", e.Status)
        Catch e As Exception
            Console.WriteLine("Exception raised!")
            Console.WriteLine("Source :{0} ", e.Source)
            Console.WriteLine("Message :{0} ", e.Message)
        End Try
    End Sub ' ReadCallBack

End Class ' WebRequest_BeginGetResponse