Namespace MyTracer
    Public Class TracerModule : Implements IHttpModule
        Public ReadOnly Property ModuleName() As String
            Get
                Return "MyTracerModule"
            End Get
        End Property

        Sub Init(ByVal app As HttpApplication) Implements _
            IHttpModule.Init
            AddHandler app.PostRequestHandlerExecute, _
                AddressOf OnPostRequestHandlerExecute
        End Sub

        Public Sub Dispose() Implements IHttpModule.Dispose
        End Sub

        Private Sub OnPostRequestHandlerExecute( _
                ByVal source As Object, ByVal e As EventArgs)
            Dim application As HttpApplication = _
                DirectCast(source, HttpApplication)
            Dim context As HttpContext = application.Context
            If context.Trace.IsEnabled Then
                Dim response As HttpResponse = context.Response
                If Not response Is Nothing Then
                    response.Filter = New TraceStream(response.Filter)
                End If
            End If
        End Sub
    End Class
End Namespace

Public Class TraceStream : Inherits MemoryStream
    Private _outputStream As Stream

    Public Sub New(ByVal outputStream As Stream)
        _outputStream = outputStream
    End Sub

Public Overrides Sub Write( _
            ByVal buffer As Byte(), ByVal offset As Integer, _
            ByVal count As Integer)
        
        Dim enc As New ASCIIEncoding
        Dim pageResponse As String = enc.GetString(buffer, offset, count)

        Dim newPageResponse As String = _ 
            TraceOutputService.Parse(pageResponse)

        Dim data() As Byte = enc.GetBytes(newPageResponse)
        _outputStream.Write(data, 0, data.Length)
    End Sub
End Class

Public Class TraceOutputServiceSection : Inherits ConfigurationSection
    <ConfigurationProperty("providers")> _
    Public ReadOnly Property Providers() As ProviderSettingsCollection
        Get
            Return DirectCast(MyBase.Item("providers"), _   
                ProviderSettingsCollection)
        End Get
    End Property

    <ConfigurationProperty("defaultProvider", _
     DefaultValue:="StandardTraceOutputProvider")> _
    Public Property DefaultProvider() As String
        Get
            Return DirectCast(MyBase.Item("defaultProvider"), String)
        End Get
        Set(ByVal value As String)
            MyBase.Item("defaultProvider") = value
        End Set
    End Property
End Class

Friend Class PageOutputInfo
    Public PageContent As String
    Public PageTrace As String
End Class

Public Class TraceOutputService
    Private Shared _provider As TraceOutputProvider = Nothing
    Private Shared _providers As TraceOutputProviderCollection = Nothing
    Private Shared _internalLock As New Object

    Public ReadOnly Property Provider() As TraceOutputProvider
        Get
            Return _provider
        End Get
    End Property

    Public ReadOnly Property Providers() As TraceOutputProviderCollection
        Get
            Return _providers
        End Get
    End Property

    Public Shared Function Parse(ByVal pageResponse As String) As String
        Dim info As PageOutputInfo = SplitPageResponse(pageResponse)

        LoadAllProviders()

        If String.IsNullOrEmpty(info.PageTrace) Then
            Return info.PageContent
        End If

        return info.PageContent & _
            _provider.PostProcess(info.PageTrace)
    End Function

    Private Shared Sub LoadAllProviders()
        If Not _provider Is Nothing Then Return
        SyncLock _internalLock
            If Not _provider Is Nothing Then Return

            Dim name As String = "system.web/traceOutputService"
            Dim section As TraceOutputServiceSection = _
                DirectCast(WebConfigurationManager.GetSection(name), _
                TraceOutputServiceSection)

            _providers = New TraceOutputProviderCollection()
            ProvidersHelper.InstantiateProviders(section.Providers, _
                _providers, GetType(TraceOutputProvider))

            _provider = _providers(section.DefaultProvider)
            If _provider Is Nothing Then
                Throw New ProviderException(
                    "Couldn’t load the default TraceOutputProvider")
            End If
        End SyncLock
    End Sub

    Private Shared Function SplitPageResponse( _
            ByVal pageResponse As String) As PageOutputInfo
        Dim info As New PageOutputInfo

        Dim beginWith As String = "<div id=""__asptrace"">"
        Dim pos As Integer = pageResponse.IndexOf(beginWith)
        If (pos < 0) Then
            info.PageContent = pageResponse
            info.PageTrace = String.Empty
            Return info
        End If

        info.PageTrace = pageResponse.Substring(pos)
        info.PageContent = pageResponse.Substring(0, pos - 1)
        Return info
    End Function
End Class