ASP.NET MVC 2.0 Application Template CAPTCHA VB.NET Code Example

The ASP.NET MVC 2.0 application template Captcha example project shows how to use the BotDetect CAPTCHA MvcCaptcha control in ASP.NET MVC 2.0 web applications.

First Time Here?

Check the BotDetect ASP.NET MVC Captcha Quickstart for key integration steps.

Starting with the default ASP.NET MVC 2.0 Visual Studio 2008 project template, the example includes all code required to add CAPTCHA validation to the Account controller Register action.

The example remembers when the CAPTCHA is successfully solved within a single registration, and doesn't display it again if there are errors with other form values (the username, for example).

You can get a new CAPTCHA using the Register action link in the top right corner of the page, and see the explanation in the Account controller code.

Download the BotDetect ASP.NET CAPTCHA Component and run this example

→ ASP.NET MVC version:

→ .NET programming language:

  • C#
  • VB.NET

Installed Location

By default, the .NET 3.5 VB.NET version of the ASP.NET MVC 2.0 application template Captcha example project is installed at:
C:\Program Files\Captcha Inc\BotDetect 4 CAPTCHA Component\Asp.Net\.NET3.5\WebApp\AspNetMvc20CaptchaExample\VBNet

You can also run it from the BotDetect Start Menu:
Programs > Captcha Inc > BotDetect 4 CAPTCHA Component > ASP.NET > DotNET 3.5 Web Applications > Run

Models\AccountModels.vb

Imports System.ComponentModel
Imports System.ComponentModel.DataAnnotations
Imports System.Globalization
Imports BotDetect.Web.Mvc

#Region "Models"
<PropertiesMustMatch("NewPassword", "ConfirmPassword", 
ErrorMessage:="The new password and confirmation password do not match.")> _
Public Class ChangePasswordModel
  Private oldPasswordValue As String
  Private newPasswordValue As String
  Private confirmPasswordValue As String

  <Required()> _
  <DataType(DataType.Password)> _
  <DisplayName("Current password")> _
  Public Property OldPassword() As String
    Get
      Return oldPasswordValue
    End Get
    Set(ByVal value As String)
      oldPasswordValue = value
    End Set
  End Property

  <Required()> _
  <ValidatePasswordLength()> _
  <DataType(DataType.Password)> _
  <DisplayName("New password")> _
  Public Property NewPassword() As String
    Get
      Return newPasswordValue
    End Get
    Set(ByVal value As String)
      newPasswordValue = value
    End Set
  End Property

  <Required()> _
  <DataType(DataType.Password)> _
  <DisplayName("Confirm new password")> _
  Public Property ConfirmPassword() As String
    Get
      Return confirmPasswordValue
    End Get
    Set(ByVal value As String)
      confirmPasswordValue = value
    End Set
  End Property
End Class

Public Class LogOnModel
  Private userNameValue As String
  Private passwordValue As String
  Private rememberMeValue As Boolean

  <Required()> _
  <DisplayName("User name")> _
  Public Property UserName() As String
    Get
      Return userNameValue
    End Get
    Set(ByVal value As String)
      userNameValue = value
    End Set
  End Property

  <Required()> _
  <DataType(DataType.Password)> _
  <DisplayName("Password")> _
  Public Property Password() As String
    Get
      Return passwordValue
    End Get
    Set(ByVal value As String)
      passwordValue = value
    End Set
  End Property

  <DisplayName("Remember me?")> _
  Public Property RememberMe() As Boolean
    Get
      Return rememberMeValue
    End Get
    Set(ByVal value As Boolean)
      rememberMeValue = value
    End Set
  End Property
End Class

<PropertiesMustMatch("Password", "ConfirmPassword", 
ErrorMessage:="The password and confirmation password do not match.")> _
Public Class RegisterModel
  Private userNameValue As String
  Private passwordValue As String
  Private confirmPasswordValue As String
  Private emailValue As String

  <Required()> _
  <DisplayName("User name")> _
  Public Property UserName() As String
    Get
      Return userNameValue
    End Get
    Set(ByVal value As String)
      userNameValue = value
    End Set
  End Property

  <Required()> _
  <DataType(DataType.EmailAddress)> _
  <DisplayName("Email address")> _
  Public Property Email() As String
    Get
      Return emailValue
    End Get
    Set(ByVal value As String)
      emailValue = value
    End Set
  End Property

  <Required()> _
  <ValidatePasswordLength()> _
  <DataType(DataType.Password)> _
  <DisplayName("Password")> _
  Public Property Password() As String
    Get
      Return passwordValue
    End Get
    Set(ByVal value As String)
      passwordValue = value
    End Set
  End Property

  <Required()> _
  <DataType(DataType.Password)> _
  <DisplayName("Confirm password")> _
  Public Property ConfirmPassword() As String
    Get
      Return confirmPasswordValue
    End Get
    Set(ByVal value As String)
      confirmPasswordValue = value
    End Set
  End Property

  ' add Captcha code as a field in the protected action Model
  Private captchaCodeValue As String

  <Required(ErrorMessage:="Retyping the characters from the picture is required.")> _
  <DisplayName("Please retype the characters from the picture")> _
  Public Property CaptchaCode() As String
    Get
      Return captchaCodeValue
    End Get
    Set(ByVal value As String)
      captchaCodeValue = value
    End Set
  End Property
End Class
#End Region

#Region "Services"
' The FormsAuthentication type is sealed and contains static members, so it is 
' difficult to
' unit test code that calls its members. The interface and helper class below 
' demonstrate
' how to create an abstract wrapper around such a type in order to make the 
' AccountController
' code unit testable.

Public Interface IMembershipService
  ReadOnly Property MinPasswordLength() As Integer

  Function ValidateUser(ByVal userName As String, ByVal password As String) As 
  Boolean
  Function CreateUser(ByVal userName As String, ByVal password As String, 
  ByVal email As String) As MembershipCreateStatus
  Function ChangePassword(ByVal userName As String, ByVal oldPassword As String, 
  ByVal newPassword As String) As Boolean
End Interface

Public Class AccountMembershipService
  Implements IMembershipService

  Private ReadOnly _provider As MembershipProvider

  Public Sub New()
    Me.New(Nothing)
  End Sub

  Public Sub New(ByVal provider As MembershipProvider)
    _provider = If(provider, Membership.Provider)
  End Sub

  Public ReadOnly Property MinPasswordLength() As Integer Implements 
  IMembershipService.MinPasswordLength
    Get
      Return _provider.MinRequiredPasswordLength
    End Get
  End Property

  Public Function ValidateUser(ByVal userName As String, 
  ByVal password As String) As Boolean Implements IMembershipService.ValidateUser
    If String.IsNullOrEmpty(userName) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "userName")
    If String.IsNullOrEmpty(password) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "password")

    Return _provider.ValidateUser(userName, password)
  End Function

  Public Function CreateUser(ByVal userName As String, ByVal password As String, 
  ByVal email As String) As MembershipCreateStatus Implements IMembershipService.CreateUser
    If String.IsNullOrEmpty(userName) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "userName")
    If String.IsNullOrEmpty(password) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "password")
    If String.IsNullOrEmpty(email) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "email")

    Dim status As MembershipCreateStatus
    _provider.CreateUser(userName, password, email, Nothing, Nothing, True, 
    Nothing, status)
    Return status
  End Function

  Public Function ChangePassword(ByVal userName As String, 
  ByVal oldPassword As String, ByVal newPassword As String) 
  As Boolean Implements IMembershipService.ChangePassword
    If String.IsNullOrEmpty(userName) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "username")
    If String.IsNullOrEmpty(oldPassword) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "oldPassword")
    If String.IsNullOrEmpty(newPassword) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "newPassword")

    ' The underlying ChangePassword() will throw an exception rather
    ' than return false in certain failure scenarios.
    Try
      Dim currentUser As MembershipUser = _provider.GetUser(userName, True)
      Return currentUser.ChangePassword(oldPassword, newPassword)
    Catch ex As ArgumentException
      Return False
    Catch ex As MembershipPasswordException
      Return False
    End Try
  End Function
End Class

Public Interface IFormsAuthenticationService
  Sub SignIn(ByVal userName As String, ByVal createPersistentCookie As Boolean)
  Sub SignOut()
End Interface

Public Class FormsAuthenticationService
  Implements IFormsAuthenticationService

  Public Sub SignIn(ByVal userName As String, ByVal createPersistentCookie As 
  Boolean) Implements IFormsAuthenticationService.SignIn
    If String.IsNullOrEmpty(userName) Then 
    Throw New ArgumentException("Value cannot be null or empty.", "userName")

    FormsAuthentication.SetAuthCookie(userName, createPersistentCookie)
  End Sub

  Public Sub SignOut() Implements IFormsAuthenticationService.SignOut
    FormsAuthentication.SignOut()
  End Sub
End Class
#End Region

#Region "Validation"
Public NotInheritable Class AccountValidation
  Public Shared Function ErrorCodeToString(ByVal createStatus As MembershipCreateStatus) As String
    ' See http://go.microsoft.com/fwlink/?LinkID=177550 for
    ' a full list of status codes.
    Select Case createStatus
      Case MembershipCreateStatus.DuplicateUserName
        Return "Username already exists. Please enter a different user name."

      Case MembershipCreateStatus.DuplicateEmail
        Return "A username for that e-mail address already exists. Please enter 
        a different e-mail address."

      Case MembershipCreateStatus.InvalidPassword
        Return "The password provided is invalid. Please enter a valid password 
        value."

      Case MembershipCreateStatus.InvalidEmail
        Return "The e-mail address provided is invalid. Please check the value 
        and try again."

      Case MembershipCreateStatus.InvalidAnswer
        Return "The password retrieval answer provided is invalid. Please check 
        the value and try again."

      Case MembershipCreateStatus.InvalidQuestion
        Return "The password retrieval question provided is invalid. Please 
        check the value and try again."

      Case MembershipCreateStatus.InvalidUserName
        Return "The user name provided is invalid. Please check the value and 
        try again."

      Case MembershipCreateStatus.ProviderError
        Return "The authentication provider returned an error. Please verify 
        your entry and try again. If the problem persists, please contact your 
        system administrator."

      Case MembershipCreateStatus.UserRejected
        Return "The user creation request has been canceled. Please verify your 
        entry and try again. If the problem persists, please contact your system 
        administrator."

      Case Else
        Return "An unknown error occurred. Please verify your entry and try 
        again. If the problem persists, please contact your system administrator.
        "
    End Select
  End Function
End Class

<AttributeUsage(AttributeTargets.Class, AllowMultiple:=True, Inherited:=False)> 
_
Public NotInheritable Class PropertiesMustMatchAttribute Inherits ValidationAttribute

  Private Const _defaultErrorMessage As String = "'{0}' and '{1}' do not match."
  Private ReadOnly _confirmProperty As String
  Private ReadOnly _originalProperty As String
  Private ReadOnly _typeId As New Object()

  Public Sub New(ByVal originalProperty As String, ByVal confirmProperty As String)
    MyBase.New(_defaultErrorMessage)

    _originalProperty = originalProperty
    _confirmProperty = confirmProperty
  End Sub

  Public ReadOnly Property ConfirmProperty() As String
    Get
      Return _confirmProperty
    End Get
  End Property

  Public ReadOnly Property OriginalProperty() As String
    Get
      Return _originalProperty
    End Get
  End Property

  Public Overrides ReadOnly Property TypeId() As Object
    Get
      Return _typeId
    End Get
  End Property

  Public Overrides Function FormatErrorMessage(ByVal name As String) As String
    Return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString, 
    OriginalProperty, ConfirmProperty)
  End Function

  Public Overrides Function IsValid(ByVal value As Object) As Boolean
    Dim properties As PropertyDescriptorCollection = TypeDescriptor.GetProperties(value)
    Dim originalValue = properties.Find(OriginalProperty, True).GetValue(value)
    Dim confirmValue = properties.Find(ConfirmProperty, True).GetValue(value)
    Return Object.Equals(originalValue, confirmValue)
  End Function
End Class

<AttributeUsage(AttributeTargets.Field Or AttributeTargets.Property, 
AllowMultiple:=False, Inherited:=True)> _
Public NotInheritable Class ValidatePasswordLengthAttribute
  Inherits ValidationAttribute

  Private Const _defaultErrorMessage As String = "'{0}' must be at least {1} 
  characters long."
  Private ReadOnly _minCharacters As Integer = Membership.Provider.
  MinRequiredPasswordLength

  Public Sub New()
    MyBase.New(_defaultErrorMessage)
  End Sub

  Public Overrides Function FormatErrorMessage(ByVal name As String) As String
    Return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString, name, 
    _minCharacters)
  End Function

  Public Overrides Function IsValid(ByVal value As Object) As Boolean
    Dim valueAsString As String = TryCast(value, String)
    Return (valueAsString IsNot Nothing) AndAlso (valueAsString.Length >= _minCharacters)
  End Function
End Class
#End Region

Since we want to include Captcha validation in the Register action, we add a string field representing the Captcha code to the related RegisterModel class declaration.

The <Required> attribute specifies that the Captcha code input field cannot be left blank (and which error message to display if it is), while the <Display> attribute declares the text description used to prompt users to type the Captcha code.

Views\Account\Register.aspx

<%@ Page Language="VB" MasterPageFile="~/Views/Shared/Site.Master" 
Inherits="System.Web.Mvc.ViewPage(Of AspNetMvc20CaptchaExampleVBNet.RegisterModel)" %>

<%@ Import Namespace="BotDetect.Web.Mvc" %>
<%@ Import Namespace="AspNetMvc20CaptchaExampleVBNet" %>
<asp:Content ID="registerTitle" ContentPlaceHolderID="TitleContent" 
runat="server">
  Register
</asp:Content>
<asp:Content ID="BotDetectStylesheets" ContentPlaceHolderID="includes" 
runat="server">
  <link href="<%= BotDetect.Web.CaptchaUrls.Absolute.LayoutStyleSheetUrl %>" 
  rel="stylesheet" type="text/css" />
</asp:Content>
<asp:Content ID="registerContent" ContentPlaceHolderID="MainContent" 
runat="server">
  <h2>
    Create a New Account</h2>
  <p>
    Use the form below to create a new account.
  </p>
  <p>
    Passwords are required to be a minimum of
    <%= ViewData("PasswordLength") %>
    characters in length.
  </p>
  <% Using Html.BeginForm("Register", "Account")%>
  <%= Html.ValidationSummary(True, "Account creation was unsuccessful. Please 
  correct the errors and try again.")%>
  <div>
    <fieldset id="RegisterFields">
      <legend>Account Information</legend>
      <div class="editor-label">
        <%= Html.LabelFor(Function(m) m.UserName) %>
      </div>
      <div class="editor-field">
        <%= Html.TextBoxFor(Function(m) m.UserName) %>
        <%= Html.ValidationMessageFor(Function(m) m.UserName) %>
      </div>
      <div class="editor-label">
        <%= Html.LabelFor(Function(m) m.Email) %>
      </div>
      <div class="editor-field">
        <%= Html.TextBoxFor(Function(m) m.Email) %>
        <%= Html.ValidationMessageFor(Function(m) m.Email) %>
      </div>
      <div class="editor-label">
        <%= Html.LabelFor(Function(m) m.Password) %>
      </div>
      <div class="editor-field">
        <%= Html.PasswordFor(Function(m) m.Password) %>
        <%= Html.ValidationMessageFor(Function(m) m.Password) %>
      </div>
      <div class="editor-label">
        <%= Html.LabelFor(Function(m) m.ConfirmPassword) %>
      </div>
      <div class="editor-field">
        <%= Html.PasswordFor(Function(m) m.ConfirmPassword) %>
        <%= Html.ValidationMessageFor(Function(m) m.ConfirmPassword) %>
      </div>
      <%' add Captcha validation controls to the protected action View
        Dim registrationCaptcha As MvcCaptcha
        registrationCaptcha = CaptchaHelper.GetRegistrationCaptcha()
        If (Not registrationCaptcha.IsSolved) Then%>
      <div class="editor-label">
        <%= Html.Captcha(registrationCaptcha) %>
        <%= Html.LabelFor(Function(m) m.CaptchaCode)%>
      </div>
      <div class="editor-field">
        <%= Html.TextBoxFor(Function(m) m.CaptchaCode)%>
        <%= Html.ValidationMessageFor(Function(m) m.CaptchaCode)%>
      </div>
      <% End If%>
      <p style="width: 195px; text-align: right;">
        <input type="submit" value="Register"/>
      </p>
    </fieldset>
  </div>
  <% End Using%>
</asp:Content>

BotDetect stylesheets are included in the generated page Header using the includes content placeholder defined in the Master page.

To keep View code simple, we delegate MvcCaptcha instance creation to a helper class, and use it along with Model fields to generate the required markup using straightforward HtmlHelper calls.

Since we want to avoid re-displaying the Captcha challenge to users after they solve it, we only call the markup generation code if the IsSolved property is not set by a previous successful Captcha validation.

Views\Shared\Site.Master

<%@ Master Language="VB" Inherits="System.Web.Mvc.ViewMasterPage" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>
    <asp:ContentPlaceHolder ID="TitleContent" runat="server" />
  </title>
  <link href="../../Content/Site.css" rel="stylesheet" type="text/css" />
  <asp:ContentPlaceHolder ID="includes" runat="server" />
</head>
<body>
  <div class="page">
    <div id="header">
      <div id="title">
        <h1>
          BotDetect CAPTCHA ASP.NET MVC 2.0 Example</h1>
      </div>
      <div id="logindisplay">
        <% Html.RenderPartial("LogOnUserControl")%>
      </div>
      <div id="menucontainer">
        <ul id="menu">
          <li>
            <%= Html.ActionLink("Home", "Index", "Home")%></li>
          <li>
            <%= Html.ActionLink("About", "About", "Home")%></li>
        </ul>
      </div>
    </div>
    <div id="main">
      <asp:ContentPlaceHolder ID="MainContent" runat="server" />
      <div id="footer">
      </div>
    </div>
  </div>
</body>
</html>

To allow easy inclusion of BotDetect stylesheets into Views which require them, the includes content placeholder should be declared in the Master page header.

Controllers\AccountController.vb

Imports System.Diagnostics.CodeAnalysis
Imports System.Security.Principal
Imports System.Web.Routing
Imports BotDetect.Web.Mvc

<HandleError()> _
Public Class AccountController
  Inherits System.Web.Mvc.Controller

  Private formsServiceValue As IFormsAuthenticationService
  Private membershipServiceValue As IMembershipService

  Public Property FormsService() As IFormsAuthenticationService
    Get
      Return formsServiceValue
    End Get
    Set(ByVal value As IFormsAuthenticationService)
      formsServiceValue = value
    End Set
  End Property

  Public Property MembershipService() As IMembershipService
    Get
      Return membershipServiceValue
    End Get
    Set(ByVal value As IMembershipService)
      membershipServiceValue = value
    End Set
  End Property

  Protected Overrides Sub Initialize(ByVal requestContext As RequestContext)
    If FormsService Is Nothing Then FormsService = New 
    FormsAuthenticationService()
    If MembershipService Is Nothing Then MembershipService = New 
    AccountMembershipService()

    MyBase.Initialize(requestContext)
  End Sub

  ' **************************************
  ' URL: /Account/LogOn
  ' **************************************

  Public Function LogOn() As ActionResult
    Return View()
  End Function

  <HttpPost()> _
  Public Function LogOn(ByVal model As LogOnModel, ByVal returnUrl As String) As 
  ActionResult
    If ModelState.IsValid Then
      If MembershipService.ValidateUser(model.UserName, model.Password) Then
        FormsService.SignIn(model.UserName, model.RememberMe)
        If Not String.IsNullOrEmpty(returnUrl) Then
          Return Redirect(returnUrl)
        Else
          Return RedirectToAction("Index", "Home")
        End If
      Else
        ModelState.AddModelError("", 
        "The user name or password provided is incorrect.")
      End If
    End If

    ' If we got this far, something failed, redisplay form
    Return View(model)
  End Function

  ' **************************************
  ' URL: /Account/LogOff
  ' **************************************

  Public Function LogOff() As ActionResult
    FormsService.SignOut()

    Return RedirectToAction("Index", "Home")
  End Function

  ' **************************************
  ' URL: /Account/Register
  ' **************************************

  Public Function Register() As ActionResult
    ViewData("PasswordLength") = MembershipService.MinPasswordLength

    ' when the View is accessed directly and not posted, we clear any
    ' remembered CAPTCHA solving state. 
    ' The users only have to solve the CAPTCHA once within a single 
    ' registration, but if they reload the Register page later,
    ' it is shown again. 
    ' Otherwise, they could register an unlimited number of accounts 
    ' within a single Session after solving the CAPTCHA only once.
    MvcCaptcha.ResetCaptcha("RegistrationCaptcha")

    Return View()
  End Function

  <HttpPost()> _
  <CaptchaValidation("CaptchaCode", "RegistrationCaptcha", 
  "Your input doesn't match displayed characters.")> _
  Public Function Register(ByVal model As RegisterModel) As ActionResult
    If ModelState.IsValid Then
      ' Attempt to register the user
      Dim createStatus As MembershipCreateStatus = MembershipService.CreateUser(
      model.UserName, model.Password, model.Email)

      If createStatus = MembershipCreateStatus.Success Then
        FormsService.SignIn(model.UserName, False)
        Return RedirectToAction("Index", "Home")
      Else
        ModelState.AddModelError("", AccountValidation.ErrorCodeToString(createStatus))
      End If
    End If

    ' If we got this far, something failed, redisplay form
    ViewData("PasswordLength") = MembershipService.MinPasswordLength
    Return View(model)
  End Function

  ' **************************************
  ' URL: /Account/ChangePassword
  ' **************************************

  <Authorize()> _
  Public Function ChangePassword() As ActionResult
    ViewData("PasswordLength") = MembershipService.MinPasswordLength
    Return View()
  End Function

  <Authorize()> _
  <HttpPost()> _
  Public Function ChangePassword(ByVal model As ChangePasswordModel) As 
  ActionResult
    If ModelState.IsValid Then
      If MembershipService.ChangePassword(User.Identity.Name, model.OldPassword, 
      model.NewPassword) Then
        Return RedirectToAction("ChangePasswordSuccess")
      Else
        ModelState.AddModelError("", 
        "The current password is incorrect or the new password is invalid.")
      End If
    End If

    ' If we got this far, something failed, redisplay form
    ViewData("PasswordLength") = MembershipService.MinPasswordLength
    Return View(model)
  End Function

  ' **************************************
  ' URL: /Account/ChangePasswordSuccess
  ' **************************************

  Public Function ChangePasswordSuccess() As ActionResult
    Return View()
  End Function
End Class

To add Captcha validation to the Register action Controller code, we perform a single line of setup in the Register action when the user GETs it, and execute the <CaptchaValidation> filter when the user POSTs it.

The filter attribute will automatically add the appropriate ModelState error if the Captcha code input doesn't match the code displayed to the user in the Captcha picture.

CaptchaHelper.vb

Imports BotDetect
Imports BotDetect.Web
Imports BotDetect.Web.UI
Imports BotDetect.Web.Mvc

Public Class CaptchaHelper

  Public Shared Function GetRegistrationCaptcha() As MvcCaptcha

    ' create the control instance
    Dim registrationCaptcha As MvcCaptcha = _
        New MvcCaptcha("RegistrationCaptcha")

    registrationCaptcha.UserInputID = "CaptchaCode"

    ' all Captcha properties are set in this event handler
    AddHandler WebFormsCaptcha.InitializedWebCaptcha, _
        AddressOf RegistrationCaptcha_InitializedWebCaptcha

    Return registrationCaptcha

  End Function

  ' event handler used for Captcha control property randomization
  Public Shared Sub RegistrationCaptcha_InitializedWebCaptcha( _
      ByVal sender As Object, _
      ByVal e As BotDetect.InitializedWebCaptchaEventArgs)

    If (e.CaptchaId <> "RegistrationCaptcha") Then
      Return
    End If

    Dim registrationCaptcha As Captcha = TryCast(sender, Captcha)

    ' fixed Captcha settings 
    registrationCaptcha.ImageSize = New System.Drawing.Size(200, 50)
    registrationCaptcha.CodeLength = 4

    ' randomized Captcha settings
    registrationCaptcha.ImageStyle = CaptchaRandomization.GetRandomImageStyle()
    registrationCaptcha.SoundStyle = CaptchaRandomization.GetRandomSoundStyle()
  End Sub

End Class

Captcha instance creation and property setting is encapsulated in this simple helper class. This separation allows application Views to stay simple regardless of the amount of Captcha customization chosen.

Global.asax.vb

' Note: For instructions on enabling IIS6 or IIS7 classic mode, 
' visit http://go.microsoft.com/?LinkId=9394802

Public Class MvcApplication
  Inherits System.Web.HttpApplication

  Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}")

    ' BotDetect requests must not be routed
    routes.IgnoreRoute("{*botdetect}", 
    New With {.botdetect = "(.*) BotDetectCaptcha\.ashx"})

    ' MapRoute takes the following parameters, in order:
    ' (1) Route name
    ' (2) URL with parameters
    ' (3) Parameter defaults
    routes.MapRoute( _
        "Default", _
        "{controller}/{action}/{id}", _
        New With {.controller = "Account", .action = "Register", .
        id = UrlParameter.Optional} _
    )

  End Sub

  Sub Application_Start()
    AreaRegistration.RegisterAllAreas()

    RegisterRoutes(RouteTable.Routes)
  End Sub
End Class

Since all BotDetect requests are handled by the BotDetect HttpHandler, ASP.NET Url Routing must be configured to ignore BotDetect requests, which can be achieved by a single line of code in Global.asax code-behind.

Web.config

<?xml version="1.0"?>
<configuration>
  <configSections>
    <sectionGroup name="system.web.extensions" type="System.Web.Configuration.
    SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, 
    Culture=neutral, PublicKeyToken=31BF3856AD364E35">
      <sectionGroup name="scripting" type="System.Web.Configuration.
      ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35">
        <section name="scriptResourceHandler" type="System.Web.Configuration.
        ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.
        5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" 
        requirePermission="false" allowDefinition="MachineToApplication"/>
        <sectionGroup name="webServices" type="System.Web.Configuration.
        ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0,
        Culture=neutral, PublicKeyToken=31BF3856AD364E35">
          <section name="jsonSerialization" type="System.Web.Configuration.
          ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.
          0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" 
          requirePermission="false" allowDefinition="Everywhere"/>
          <section name="profileService" type="System.Web.Configuration.
          ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0,
          Culture=neutral, PublicKeyToken=31BF3856AD364E35" 
          requirePermission="false" allowDefinition="MachineToApplication"/>
          <section name="authenticationService" type="System.Web.Configuration.
          ScriptingAuthenticationServiceSection, System.Web.Extensions, 
          Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" 
          requirePermission="false" allowDefinition="MachineToApplication"/>
          <section name="roleService" type="System.Web.Configuration.
          ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, 
          Culture=neutral, PublicKeyToken=31BF3856AD364E35" 
          requirePermission="false" allowDefinition="MachineToApplication"/>
        </sectionGroup>
      </sectionGroup>
    </sectionGroup>
    <!-- Register the BotDetect configuration section -->
    <section name="botDetect" requirePermission="false" 
    type="BotDetect.Configuration.BotDetectConfigurationSection, BotDetect"/>
  </configSections>
  <connectionStrings>
    <add name="ApplicationServices" connectionString="data source=.\SQLEXPRESS;
    Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User 
    Instance=true" providerName="System.Data.SqlClient"/>
  </connectionStrings>
  <system.web>
    <compilation debug="false">
      <assemblies>
        <add assembly="System.Core, Version=3.5.0.0, Culture=neutral, 
        PublicKeyToken=B77A5C561934E089"/>
        <add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35"/>
        <add assembly="System.Web.Abstractions, Version=3.5.0.0, Culture=neutral,
        PublicKeyToken=31BF3856AD364E35"/>
        <add assembly="System.Web.Routing, Version=3.5.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35"/>
        <add assembly="System.Web.Mvc, Version=2.0.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35"/>
      </assemblies>
    </compilation>
    <authentication mode="Forms">
      <forms loginUrl="~/Account/LogOn" timeout="2880" />
    </authentication>
    <membership>
      <providers>
        <clear/>
        <add name="AspNetSqlMembershipProvider" type="System.Web.Security.
        SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, 
        PublicKeyToken=b03f5f7f11d50a3a" 
        connectionStringName="ApplicationServices" 
        enablePasswordRetrieval="false" enablePasswordReset="true" 
        requiresQuestionAndAnswer="false" requiresUniqueEmail="false" 
        passwordFormat="Hashed" maxInvalidPasswordAttempts="5" 
        minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" 
        passwordAttemptWindow="10" passwordStrengthRegularExpression="" 
        applicationName="/"/>
      </providers>
    </membership>
    <profile>
      <providers>
        <clear/>
        <add name="AspNetSqlProfileProvider" type="System.Web.Profile.
        SqlProfileProvider, System.Web, Version=2.0.0.0, Culture=neutral, 
        PublicKeyToken=b03f5f7f11d50a3a" 
        connectionStringName="ApplicationServices" applicationName="/"/>
      </providers>
    </profile>
    <roleManager enabled="false">
      <providers>
        <clear/>
        <add connectionStringName="ApplicationServices" applicationName="/" 
        name="AspNetSqlRoleProvider" type="System.Web.Security.SqlRoleProvider, 
        System.Web, Version=2.0.0.0, Culture=neutral, 
        PublicKeyToken=b03f5f7f11d50a3a"/>
        <add applicationName="/" name="AspNetWindowsTokenRoleProvider" 
        type="System.Web.Security.WindowsTokenRoleProvider, System.Web, 
        Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
      </providers>
    </roleManager>
    <!-- make sure Session State is enabled -->
    <pages enableSessionState="true">
      <controls>
        <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.
        Extensions, Version=3.5.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35"/>
        <add tagPrefix="asp" namespace="System.Web.UI.WebControls" 
        assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35"/>
      </controls>
      <namespaces>
        <add namespace="System.Web.Mvc"/>
        <add namespace="System.Web.Mvc.Ajax"/>
        <add namespace="System.Web.Mvc.Html"/>
        <add namespace="System.Web.Routing"/>
        <add namespace="System.Collections.Generic"/>
        <!-- add BotDetect namespaces for coding convenience -->
        <add namespace="BotDetect"/>
        <add namespace="BotDetect.Web"/>
        <add namespace="BotDetect.Web.UI"/>
        <add namespace="BotDetect.Web.Mvc"/>
      </namespaces>
    </pages>
    <!-- configure Session State for BotDetect use -->
    <sessionState mode="InProc" cookieless="AutoDetect" timeout="20" 
    sessionIDManagerType="BotDetect.Web.CustomSessionIdManager, BotDetect"/>
    <httpHandlers>
      <remove verb="*" path="*.asmx"/>
      <add verb="*" path="*.asmx" validate="false" type="System.Web.Script.
      Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      <add verb="*" path="*_AppService.axd" validate="false" type="System.Web.
      Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.
      0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      <add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.
      ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35" validate="false"/>
      <add verb="*" path="*.mvc" validate="false" type="System.Web.Mvc.
      MvcHttpHandler, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, 
      PublicKeyToken=31BF3856AD364E35"/>
      <!-- register HttpHandler used for BotDetect Captcha requests -->
      <add verb="GET" path="BotDetectCaptcha.ashx" 
      type="BotDetect.Web.CaptchaHandler, BotDetect"/>
    </httpHandlers>
    <httpModules>
      <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.
      Web.Extensions, Version=3.5.0.0, Culture=neutral, 
      PublicKeyToken=31BF3856AD364E35"/>
      <add name="UrlRoutingModule" type="System.Web.Routing.UrlRoutingModule, 
      System.Web.Routing, Version=3.5.0.0, Culture=neutral, 
      PublicKeyToken=31BF3856AD364E35"/>
    </httpModules>
  </system.web>
  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" warningLevel="4" 
      type="Microsoft.CSharp.CSharpCodeProvider, System, Version=2.0.0.0, 
      Culture=neutral, PublicKeyToken=b77a5c561934e089">
        <providerOption name="CompilerVersion" value="v3.5"/>
        <providerOption name="WarnAsError" value="false"/>
      </compiler>
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" 
      warningLevel="4" type="Microsoft.VisualBasic.VBCodeProvider, System, 
      Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
        <providerOption name="CompilerVersion" value="v3.5"/>
        <providerOption name="OptionInfer" value="true"/>
        <providerOption name="WarnAsError" value="false"/>
      </compiler>
    </compilers>
  </system.codedom>
  <system.web.extensions/>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <modules runAllManagedModulesForAllRequests="true">
      <remove name="ScriptModule"/>
      <remove name="UrlRoutingModule"/>
      <add name="ScriptModule" preCondition="managedHandler" type="System.Web.
      Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      <add name="UrlRoutingModule" type="System.Web.Routing.UrlRoutingModule, 
      System.Web.Routing, Version=3.5.0.0, Culture=neutral, 
      PublicKeyToken=31BF3856AD364E35"/>
    </modules>
    <handlers>
      <remove name="WebServiceHandlerFactory-Integrated"/>
      <remove name="ScriptHandlerFactory"/>
      <remove name="ScriptHandlerFactoryAppServices"/>
      <remove name="ScriptResource"/>
      <remove name="MvcHttpHandler"/>
      <remove name="UrlRoutingHandler"/>
      <add name="ScriptHandlerFactory" verb="*" path="*.asmx" 
      preCondition="integratedMode" type="System.Web.Script.Services.
      ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      <add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.
      axd" preCondition="integratedMode" type="System.Web.Script.Services.
      ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      <add name="ScriptResource" preCondition="integratedMode" verb="GET,HEAD" 
      path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, 
      System.Web.Extensions, Version=3.5.0.0, Culture=neutral, 
      PublicKeyToken=31BF3856AD364E35"/>
      <add name="MvcHttpHandler" preCondition="integratedMode" verb="*" path="*.
      mvc" type="System.Web.Mvc.MvcHttpHandler, System.Web.Mvc, Version=2.0.0.0, 
      Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      <add name="UrlRoutingHandler" preCondition="integratedMode" verb="*" 
      path="UrlRouting.axd" type="System.Web.HttpForbiddenHandler, System.Web, 
      Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
      <!-- register HttpHandler used for BotDetect Captcha requests -->
      <remove name="BotDetectCaptchaHandler"/>
      <add name="BotDetectCaptchaHandler" preCondition="integratedMode" 
      verb="GET" path="BotDetectCaptcha.ashx" 
      type="BotDetect.Web.CaptchaHandler, BotDetect"/>
    </handlers>
  </system.webServer>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" 
        publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <botDetect helpLinkEnabled="true" helpLinkMode="image" />
</configuration>

The application's web.config file includes the standard BotDetect HttpHandler and Session state configuration elements.