How To Create A Module In Visual Basic

Adding New VB .NET Module At this stage we already completed the VB .NET web service project. Next, let add another project for the asynchronous web access. Add a new project. Select Class Library project template and you can use AsyncModuleVB as the project name.

Change the default given class name to AsyncModule to reflect the application to be developed.

Imports System

Imports System.Web

Imports System.Threading

Imports System.Text.RegularExpressions

Public Class AsyncModule

Implements IHttpModule

' shared data members

Shared counter As Integer = 0

Shared modCounter As Integer = 0

Const RedirectLocation As String = "accessdenied.aspx"

' instance data members

Dim instanceCounter As Integer

Dim isAuthorized As Boolean

Dim ctx As HttpContext

Dim locationRegex As Regex = New Regex(RedirectLocation, RegexOptions.IgnoreCase)

Public Sub Dispose() Implements IHttpModule.Dispose

' nothing to do

End Sub

Public Sub Init( ByVal app As HttpApplication) Implements IHttpModule.Init

' register for our async event

        app.AddOnAuthorizeRequestAsync( New BeginEventHandler( AddressOf AsyncBeginHandler), New EndEventHandler( AddressOf AsyncEndHandler))

' add a sync EndRequest handler to explain what happened if

' access is denied

AddHandler app.EndRequest, New EventHandler( AddressOf OnEndRequest)

Dim modCount As Integer = Interlocked.Increment(modCounter)

        TraceHelper.WriteLine( "AsyncModule.Init: Initializing the module instance..." , modCount)

End Sub

Public Function AsyncBeginHandler( ByVal src As Object , ByVal e As EventArgs, ByVal cb As AsyncCallback, ByVal extraData As Object ) As IAsyncResult

Dim app As HttpApplication = CType (src, HttpApplication)

' per-request init

        instanceCounter = Interlocked.Increment(counter)

        isAuthorized = False

        ctx = app.Context

' let anyone into the access denied page

Dim m As Match = locationRegex.Match(ctx.Request.FilePath)

' is it something other than accessdenied.aspx? Check authorization...

If Not m.Success Then

' create service proxy, async result, and callback

Dim authServ As New AuthorizationService.Service1

Dim myAr As MyAsyncResult = New MyAsyncResult(cb, authServ, instanceCounter)

Dim myCb As New AsyncCallback( AddressOf WebServiceAsyncCallback)

' start async call

            TraceHelper.WriteLine( "AsyncModule.AsyncBeginHandler: Begin the authorization..." , instanceCounter)

            authServ.BeginIsAuthorized(ctx.User.Identity.Name, myCb, myAr)

Return myAr

' otherwise, complete synchronously

Else

            isAuthorized = True

            TraceHelper.WriteLine( "AsyncModule.AsyncBeginHandler: Request for accessdenied.aspx page, skipping..." , instanceCounter)

Return New MyAsyncResult( Nothing , Nothing , True , True , Nothing , instanceCounter)

End If

End Function

Public Sub AsyncEndHandler( ByVal ar As IAsyncResult)

Dim myAr As MyAsyncResult = CType (ar, MyAsyncResult)

        TraceHelper.WriteLine( "AsyncModule.AsyncEndHandler: Ending the authorization..." , instanceCounter)

' if this user isn't authorized, then bail out

If Not isAuthorized Then

            ctx.Response.StatusCode = 403

            ctx.ApplicationInstance.CompleteRequest()

            TraceHelper.WriteLine( "AsyncModule.AsyncEndHandler: Request Rejected..." , instanceCounter)

End If

' clear variables

        ctx = Nothing

        instanceCounter = -1

        isAuthorized = False

        myAr.EndOp() ' throw if necessary

End Sub

Public Sub WebServiceAsyncCallback( ByVal ar As IAsyncResult)

Dim myAr As MyAsyncResult = CType (ar.AsyncState, MyAsyncResult)

Dim authServ As AuthorizationService.Service1 = CType (myAr.AsyncState, AuthorizationService.Service1)

' get back result

        isAuthorized = authServ.EndIsAuthorized(ar)

        TraceHelper.WriteLine( "AsyncModule.WebServiceAsyncCallback: WebService call completed..." , instanceCounter)

' tell ASP.NET we're done

Dim cnt As Integer = instanceCounter

        TraceHelper.WriteLine( "AsyncModule.WebServiceAsyncCallback: Begin notifing ASP.NET..." , cnt)

        myAr.Complete( False , isAuthorized, Nothing )

        TraceHelper.WriteLine( "AsyncModule.WebServiceAsyncCallback: End notifing ASP.NET..." , cnt)

End Sub

Public Sub OnEndRequest( ByVal src As Object , ByVal E As EventArgs)

Dim app As HttpApplication = CType (src, HttpApplication)

' did we block someone?

If app.Response.StatusCode = 403 Then

            app.Response.Redirect(RedirectLocation, False )

End If

End Sub

End Class

You can use the MyAsyncResult as the module name.

Add/edit the code as shown below. This code implements the IAsyncResult interface.

Imports System

Imports System.Threading

Imports System.Diagnostics

' Implementation of IAsyncResult

Public Class MyAsyncResult

Implements IAsyncResult

' data members

Dim cb As AsyncCallback

Dim state As Object

Dim completed As Boolean

Dim completedSync As Boolean

Dim result As Object

Dim err As Exception

Dim counter As Integer

Public Sub New ( ByVal callb As AsyncCallback, ByVal st As Object , ByVal cnt As Integer )

Me .cb = callb

Me .state = st

Me .counter = cnt

End Sub

' constructor with predefined results,

' useful for errors that occur before async work is done

Public Sub New ( ByVal callb As AsyncCallback, ByVal st As Object , ByVal complete As Boolean , ByVal res As Object , ByVal e As Exception, ByVal cnt As Integer )

Me .cb = callb

Me .state = st

Me .completed = complete

Me .completedSync = Me .completed

Me .result = res

Me .err = e

Me .counter = cnt

If Not IsNothing(cb) Then

            cb( Me )

End If

If Me .completed Then

            TraceHelper.WriteLine( "MyAsyncResult.New: MyAsyncResult completed sync" , counter)

End If

End Sub

Public ReadOnly Property AsyncState() As Object Implements System.IAsyncResult.AsyncState

Get

Return state

End Get

End Property

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

Get

Return Nothing ' Wait not Supported

End Get

End Property

Public ReadOnly Property CompletedSynchronously() As Boolean Implements System.IAsyncResult.CompletedSynchronously

Get

Return completedSync

End Get

End Property

Public ReadOnly Property IsCompleted() As Boolean Implements System.IAsyncResult.IsCompleted

Get

Return completed

End Get

End Property

' non IAsyncResult Stuff

Public ReadOnly Property AsyncError() As Exception

Get

Return err

End Get

End Property

Public Sub Complete( ByVal sync As Boolean , ByVal res As Object , ByVal e As Exception)

        TraceHelper.WriteLine( "MyAsyncResult.Complete: MyAsyncResult.Complete called" , counter)

        completed = True

        completedSync = sync

        result = res

        err = e

If Not IsNothing(cb) Then

            cb( Me )

End If

End Sub

Public Function EndOp() As Object

If Not IsNothing(err) Then

Throw New Exception( "AsyncOperation failed" , err)

End If

Return result

End Function

End Class

Next, add the helper class that will dump messages. You can use TraceHelper as the class name.

Add/edit the code as given below. This code just printing a message related to the asynchronous operations.

Imports System

Imports System.Threading

Imports System.Diagnostics

Public Class TraceHelper

Public Shared Sub WriteLine( ByVal msg As String , ByVal cnt As Integer )

Dim tid As Integer = Thread.CurrentThread.ManagedThreadId

        Trace.WriteLine( String .Format( "TraceHelper.WriteLine: ThreadId: {0} Counter: {1} Msg: {2}" , tid, cnt, msg))

End Sub

End Class

How To Create A Module In Visual Basic

Source: https://www.winsocketdotnetworkprogramming.com/xmlwebservicesaspnetworkprogramming11l.html

Posted by: johnsonbefteeprishe.blogspot.com

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