ASP.NET

<![CDATA[<%@ WebHandler Language="VB" Class="SearchHttpHandler" %>]]>

Option Strict On

Imports System.Threading
Imports System.IO
Imports System.Net

Public Class SearchHttpHandler
	Implements IHttpAsyncHandler
	Implements IReadOnlySessionState

	'---------------------------------------------------------------------------------------
	
	Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
	End Sub

	
	'---------------------------------------------------------------------------------------

	Function BeginProcessRequest(ByVal context As System.Web.HttpContext, ByVal cb As System.AsyncCallback, ByVal extraData As Object) As System.IAsyncResult Implements IHttpAsyncHandler.BeginProcessRequest

		context.Response.Write("Started on thread: " & _
			Threading.Thread.CurrentThread.ManagedThreadId & " - " & _
			Threading.Thread.CurrentThread.IsThreadPoolThread.ToString & "<br />")

		'Instantiate the AsyncResult object that'll give us a hold to the context and the callback		
		Dim theAsyncResult As New SearchAsyncResult(context, cb, extraData)
		theAsyncResult.Search()
		Return theAsyncResult
				
	End Function

	'---------------------------------------------------------------------------------------

	Sub EndProcessRequest(ByVal result As System.IAsyncResult) Implements IHttpAsyncHandler.EndProcessRequest
		
		Dim theObj As SearchAsyncResult = DirectCast(result, SearchAsyncResult)
		theObj.Context.Response.Write("Ended on thread: " & _
			Threading.Thread.CurrentThread.ManagedThreadId & " - " & _
			Threading.Thread.CurrentThread.IsThreadPoolThread.ToString)
		
	End Sub

	'---------------------------------------------------------------------------------------

	Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
		Get
			Return False
		End Get
	End Property

End Class

'======================================================================================
'======================================================================================

Public Class SearchAsyncResult
	Implements IAsyncResult
	
	Public Context As HttpContext

	Private mASPNETCallback As AsyncCallback
	Private mExtraData As Object
	Private mIsCompleted As Boolean
	Private mAsyncWaitHandle As ManualResetEvent
	Private mRequest As HttpWebRequest
	
	Private mQuery As String
	
	'-------------------------------------------------------------
	
	Public Sub New(ByVal context As HttpContext, ByVal ASPNETCallback As AsyncCallback, ByVal ExtraData As Object)
		Me.Context = context
		mASPNETCallback = ASPNETCallback
		mExtraData = ExtraData
	End Sub

	'-------------------------------------------------------------

	Public Sub Search()
		
		If Context.Request.QueryString("q") IsNot Nothing Then
			mQuery = Context.Request.QueryString("q")
		End If
				
		'Return "No Results" if there is no query
		If mQuery = "" Then
			Context.Response.Write("No Results")
			CompleteRequest()
			Exit Sub
		End If
		
		'Otherwise, make an async call
		Dim URL As String = "xxxxxxx?q=" & mQuery
		mRequest = DirectCast(WebRequest.Create(URL), HttpWebRequest)

		mRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)"
		mRequest.Method = "GET"

		mRequest.BeginGetResponse(AddressOf SearchCallback, Nothing)
		
	End Sub
	
	'-------------------------------------------------------------

	Private Sub SearchCallback(ByVal ar As IAsyncResult)
		
		Dim WebResp As WebResponse = mRequest.EndGetResponse(ar)
		Dim sReader As New StreamReader(WebResp.GetResponseStream())
		Dim result As String = sReader.ReadToEnd()
		
		Context.Response.Write(result)
		
		CompleteRequest()
		
	End Sub
	
	'-------------------------------------------------------------
	
	Private Sub CompleteRequest()
		
		mIsCompleted = True
		SyncLock Me
			If mAsyncWaitHandle IsNot Nothing Then
				mAsyncWaitHandle.Set()
			End If
		End SyncLock
		If mASPNETCallback IsNot Nothing Then
			mASPNETCallback(Me)
		End If
		
	End Sub
	
	'---------------------------------------------------------------------
	
#Region "Implementation of IAsyncResult dummy members"
	
	Public ReadOnly Property AsyncState() As Object Implements System.IAsyncResult.AsyncState
		Get
			Return mExtraData
		End Get
	End Property

	Public ReadOnly Property AsyncWaitHandle() As System.Threading.WaitHandle Implements System.IAsyncResult.AsyncWaitHandle
		Get

			SyncLock Me
				If mAsyncWaitHandle Is Nothing Then
					mAsyncWaitHandle = New ManualResetEvent(False)
				End If
				Return mAsyncWaitHandle
			End SyncLock

		End Get
	End Property

	Public ReadOnly Property CompletedSynchronously() As Boolean Implements System.IAsyncResult.CompletedSynchronously
		Get
			Return False
		End Get
	End Property

	Public ReadOnly Property IsCompleted() As Boolean Implements System.IAsyncResult.IsCompleted
		Get
			Return mIsCompleted
		End Get
	End Property
	
#End Region

	'---------------------------------------------------------------------

End Class	'SearchAsyncResult