ASP.NET MVC 3.0 Application Template CAPTCHA VB.NET Code Example

The ASP.NET MVC 3.0 application template Captcha example project shows how to use the BotDetect CAPTCHA MvcCaptcha control in ASP.NET MVC web applications.

First Time Here?

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

Starting with the default ASP.NET MVC 3.0 Visual Studio 2010 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 4.0 VB.NET version of the ASP.NET MVC 3.0 application template Captcha example project is installed at:
C:\Program Files\Captcha Inc\BotDetect 4 CAPTCHA Component\Asp.Net\.NET4.0\WebApp\AspNetMvc30CaptchaExample\VBNet

You can also run it from the BotDetect Start Menu:
Programs > Captcha Inc > BotDetect 4 CAPTCHA Component > ASP.NET > DotNET 4.0 Web Applications > Run

Models\AccountModels.vb

Imports System.ComponentModel
Imports System.ComponentModel.DataAnnotations
Imports System.Globalization

Public Class ChangePasswordModel
  Private oldPasswordValue As String
  Private newPasswordValue As String
  Private confirmPasswordValue As String

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

  <Required()> _
  <StringLength(100, 
  ErrorMessage:="The {0} must be at least {2} characters long.", 
  MinimumLength:=6)> _
  <DataType(DataType.Password)> _
  <Display(Name:="New password")> _
  Public Property NewPassword() As String
    Get
      Return newPasswordValue
    End Get
    Set(ByVal value As String)
      newPasswordValue = value
    End Set
  End Property

  <DataType(DataType.Password)> _
  <Display(Name:="Confirm new password")> _
  <Compare("NewPassword", 
  ErrorMessage:="The new password and confirmation password do not match.")> _
  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()> _
  <Display(Name:="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)> _
  <Display(Name:="Password")> _
  Public Property Password() As String
    Get
      Return passwordValue
    End Get
    Set(ByVal value As String)
      passwordValue = value
    End Set
  End Property

  <Display(Name:="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

Public Class RegisterModel
  Private userNameValue As String
  Private passwordValue As String
  Private confirmPasswordValue As String
  Private emailValue As String

  <Required()> _
  <Display(Name:="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)> _
  <Display(Name:="Email address")> _
  Public Property Email() As String
    Get
      Return emailValue
    End Get
    Set(ByVal value As String)
      emailValue = value
    End Set
  End Property

  <Required()> _
  <StringLength(100, 
  ErrorMessage:="The {0} must be at least {2} characters long.", 
  MinimumLength:=6)> _
  <DataType(DataType.Password)> _
  <Display(Name:="Password")> _
  Public Property Password() As String
    Get
      Return passwordValue
    End Get
    Set(ByVal value As String)
      passwordValue = value
    End Set
  End Property

  <DataType(DataType.Password)> _
  <Display(Name:="Confirm password")> _
  <Compare("Password", 
  ErrorMessage:="The password and confirmation password do not match.")> _
  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

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.vbhtml

@ModelType AspNetMvc30CaptchaExampleVBNet.RegisterModel
@Imports BotDetect.Web.Mvc
@Imports AspNetMvc30CaptchaExampleVBNet
@Code
  ViewData("Title") = "Register"
End Code
@* add BotDetect header includes *@
@Section BotDetectStyles
  <link href="@BotDetect.Web.CaptchaUrls.Absolute.LayoutStyleSheetUrl" 
  rel="stylesheet" type="text/css" />
End Section
<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 @Membership.
  MinRequiredPasswordLength
  characters in length.
</p>
<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" 
type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" 
type="text/javascript"></script>
@Using Html.BeginForm("Register", "Account")
  @Html.ValidationSummary(True, 
  "Account creation was unsuccessful. Please correct the errors and try again.")
  @<div>
    <fieldset>
      <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 *@
      @Code Dim registrationCaptcha As MvcCaptcha
        registrationCaptcha = CaptchaHelper.GetRegistrationCaptcha()
      End Code
      @If (Not registrationCaptcha.IsSolved) Then
      @:<div class="editor-label">
        @Html.LabelFor(Function(m) m.CaptchaCode) 
        @Html.Captcha(registrationCaptcha) 
      @:</div>             
      @:<divclass="editor-field">
        @Html.TextBoxFor(Function(m) m.CaptchaCode)
        @Html.ValidationMessageFor(Function(m) m.CaptchaCode)
      @:</div>
      End If
      <p style="width: 210px; text-align: right;">
        <input type="submit" value="Register" />
      </p>
    </fieldset>
  </div>
End Using

Following ASP.NET MVC 3.0 Captcha View instructions, the BotDetectStyles section includes required BotDetect stylesheets in the generated page header.

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\_Layout.vbhtml

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8" />
  <title>@ViewData("Title")</title>
  <link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" 
  type="text/css" />
  <script src="@Url.Content("~/Scripts/jquery-1.5.1.min.js")" 
  type="text/javascript"></script>
  <script src="@Url.Content("~/Scripts/modernizr-1.7.min.js")" 
  type="text/javascript"></script>
  @* allow BotDetect stylesheet includes in selected Views *@
  @RenderSection("BotDetectStyles", required:=False)
</head>
<body>
  <div class="page">
    <header>
            <div id="title">
                <h1>BotDetect CAPTCHA ASP.NET MVC 3.0 Example</h1>
            </div>
            <div id="logindisplay">
                @Html.Partial("_LogOnPartial")
            </div>
            <nav>
                <ul id="menu">
                    <li>@Html.ActionLink("Home", "Index", "Home")</li>
                    <li>@Html.ActionLink("About", "About", "Home")</li>
                </ul>
            </nav>
        </header>
    <section id="main">
            @RenderBody()
        </section>
    <footer>
        </footer>
  </div>
</body>
</html>

To allow easy inclusion of BotDetect stylesheets into Views which require them, the BotDetectStyles section was declared in the layout template header.

Controllers\AccountController.vb

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

Public Class AccountController
  Inherits System.Web.Mvc.Controller

  '
  ' GET: /Account/LogOn

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

  '
  ' POST: /Account/LogOn

  <HttpPost()> _
  Public Function LogOn(ByVal model As LogOnModel, ByVal returnUrl As String) As 
  ActionResult
    If ModelState.IsValid Then
      If Membership.ValidateUser(model.UserName, model.Password) Then
        FormsAuthentication.SetAuthCookie(model.UserName, model.RememberMe)
        If Url.IsLocalUrl(returnUrl) AndAlso returnUrl.Length > 1 AndAlso 
        returnUrl.StartsWith("/") _
           AndAlso Not returnUrl.StartsWith("//") 
           AndAlso Not returnUrl.StartsWith("/\\") 
        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

  '
  ' GET: /Account/LogOff

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

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

  '
  ' GET: /Account/Register
  Public Function Register() As ActionResult

    ' 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

  '
  ' POST: /Account/Register

  <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
      Membership.CreateUser(model.UserName, model.Password, model.Email, Nothing,
      Nothing, True, Nothing, createStatus)

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

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

  '
  ' GET: /Account/ChangePassword

  <Authorize()> _
  Public Function ChangePassword() As ActionResult
    Return View()
  End Function

  '
  ' POST: /Account/ChangePassword

  <Authorize()> _
  <HttpPost()> _
  Public Function ChangePassword(ByVal model As ChangePasswordModel) As 
  ActionResult
    If ModelState.IsValid Then
      ' ChangePassword will throw an exception rather
      ' than return false in certain failure scenarios.
      Dim changePasswordSucceeded As Boolean

      Try
        Dim currentUser As MembershipUser = Membership.GetUser(User.Identity.Name, 
        True)
        changePasswordSucceeded = currentUser.ChangePassword(model.OldPassword, 
        model.NewPassword)
      Catch ex As Exception
        changePasswordSucceeded = False
      End Try

      If changePasswordSucceeded 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
    Return View(model)
  End Function

  '
  ' GET: /Account/ChangePasswordSuccess

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

#Region "Status Code"
  Public 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 "User name already exists. Please enter a different user name."

      Case MembershipCreateStatus.DuplicateEmail
        Return "A user name 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 Region

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 BotDetect.Web.Mvc.MvcCaptcha = _
        New BotDetect.Web.Mvc.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 RegisterGlobalFilters(ByVal filters As GlobalFilterCollection)
    filters.Add(New HandleErrorAttribute())
  End Sub

  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()

    RegisterGlobalFilters(GlobalFilters.Filters)
    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"?>
<!--
  For more information on how to configure your ASP.NET application, please 
  visit
  http://go.microsoft.com/fwlink/?LinkId=152368
  -->

<configuration>
  <configSections>
    <!-- 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>
  <appSettings>
    <add key="webpages:Version" value="1.0.0.0"/>
    <add key="ClientValidationEnabled" value="true"/>
    <add key="UnobtrusiveJavaScriptEnabled" value="true"/>
  </appSettings>
  <system.web>
    <compilation debug="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral,
        PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, 
        PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.WebPages, Version=1.0.0.0, 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" connectionStringName="ApplicationServices"
             enablePasswordRetrieval="false" enablePasswordReset="true" 
             requiresQuestionAndAnswer="false" requiresUniqueEmail="false"
             maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" 
             minRequiredNonalphanumericCharacters="0" 
             passwordAttemptWindow="10"
             applicationName="/" />
      </providers>
    </membership>
    <profile>
      <providers>
        <clear/>
        <add name="AspNetSqlProfileProvider" type="System.Web.Profile.
        SqlProfileProvider" connectionStringName="ApplicationServices" 
        applicationName="/" />
      </providers>
    </profile>
    <roleManager enabled="false">
      <providers>
        <clear/>
        <add name="AspNetSqlRoleProvider" type="System.Web.Security.
        SqlRoleProvider" connectionStringName="ApplicationServices" 
        applicationName="/" />
        <add name="AspNetWindowsTokenRoleProvider" type="System.Web.Security.
        WindowsTokenRoleProvider" applicationName="/" />
      </providers>
    </roleManager>
    <!-- make sure Session State is enabled -->
    <pages enableSessionState="true">
      <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.Web.WebPages" />
      </namespaces>
    </pages>
    <!-- configure Session State for BotDetect use -->
    <sessionState mode="InProc" cookieless="AutoDetect" timeout="20" 
    sessionIDManagerType="BotDetect.Web.CustomSessionIdManager, BotDetect"/>
    <httpHandlers>
      <!-- register HttpHandler used for BotDetect Captcha requests -->
      <add verb="GET" path="BotDetectCaptcha.ashx" 
      type="BotDetect.Web.CaptchaHandler, BotDetect"/>
    </httpHandlers>
  </system.web>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <modules runAllManagedModulesForAllRequests="true"/>
    <handlers>
      <!-- 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="1.0.0.0-2.0.0.0" newVersion="3.0.0.0" />
      </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.