ASP.NET MVC Captcha

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ASP.NET MVC Captcha

I was looking for an ASP.NET MVC Captcha control and stumbled upon Nick Berardi's (http://www.coderjournal.com/2008/06/mvc-captcha-for-preview-release-3/).

First of all I'm using IIS7 and had trouble getting the HttpHandler to register properly. I ended up with the following steps to get it to work:

Add <add verb="GET" path="captcha.ashx" validate="false" type="ManagedFusion.Web.Handlers.CaptchaImageHandler, ManagedFusion.Web.Captcha" /> to <httpHandlers> in Web.config
Add <add name="CaptchaImageHandler" verb="GET" path="captcha.ashx" type="ManagedFusion.Web.Handlers.CaptchaImageHandler, ManagedFusion.Web.Captcha" /> to the <handlers> section within <system.webserver> in Web.config
Add routes.IgnoreRoute("{handler}.ashx"); to Global.asax

So that got it working, but there were a few pieces of functionality I felt were missing:

1) I wanted the ability to style the CaptchaTextBox

The site I'm working with is pretty design intensive and I needed a way to inject CSS information into the CaptchaTextBox Html Helper. I reworked the CaptchaHelper and modified the CaptchaTextBox as well as added some overloads:

        1: public static string CaptchaTextBox(this HtmlHelper helper, string name)         

       2: {             

       3:     return helper.CaptchaTextBox(name, null);         

       4: }

       5: public static string CaptchaTextBox(this HtmlHelper helper, string name, 

       6:     Object htmlAttributes)

       7: {

       8:     return helper.CaptchaTextBox(name, 

       9:         ((IDictionary<string, object>)new RouteValueDictionary(htmlAttributes)));         

}         

public static string CaptchaTextBox(this HtmlHelper helper, string name,

 IDictionary<String, Object> htmlAttributes)         

{             

    ModelState state;             

    TagBuilder builder = new TagBuilder("input");             

    builder.MergeAttributes<string, object>(htmlAttributes);             

    builder.MergeAttribute("type", "text");             

    builder.MergeAttribute("name", name);             

    builder.MergeAttribute("id", name);             

    builder.MergeAttribute("value", "");             

    builder.MergeAttribute("maxlength", 

        ManagedFusion.Web.Controls.CaptchaImage.TextLength.ToString());             

    builder.MergeAttribute("autocomplete", "off");             

    

    if (helper.ViewData.ModelState.TryGetValue(name, out state) 

        && (state.Errors.Count > 0))             

    {                

        builder.AddCssClass("input-validation-error");             

    }             

    return builder.ToString(TagRenderMode.SelfClosing);         

}

I got the TagBuilder idea from checking out the Reflector on System.Web.MVC. Pretty cool stuff there. So now I can use the CaptchaTextBox like so:

<%= Html.CaptchaTextBox("captcha", new { @class = "field" })%>

2) I wanted the CaptchaValidationAttribute to invalidate my Model if the captcha isn't valid

(instead of inject a captchaValid with a value of false into my routedata which is what it does off the shelf)

For this I modified the CaptchaValidationAttribute class. The first thing I did was make add an ErrorMessage string property. Then I modified the OnActionExecutingContext method to look like this:

       1: public override void OnActionExecuting(ActionExecutingContext filterContext)         

       2: {             

       3:     // get the guid from the post back             

       4:     string guid = filterContext.HttpContext.Request.Form["captcha-guid"];             

       5:     // check for the guid because it is required from the 

       6: //rest of the opperation             

       7:     if (String.IsNullOrEmpty(guid))            

       8:     {                 

       9:         filterContext.Controller.ViewData.ModelState

      10:             .AddModelError(Field, ErrorMessage);                 

      11:         return;             

      12:     }            

      13:     // get values             

      14:     CaptchaImage image = CaptchaImage.GetCachedCaptcha(guid);             

      15:     string actualValue = filterContext.HttpContext.Request.Form[Field];             

      16:     string expectedValue = image == null ? String.Empty : image.Text;            

      17:     // removes the captch from cache so it cannot be used again             

      18:     filterContext.HttpContext.Cache.Remove(guid);            

      19:     // validate the captch             

      20:     if (String.IsNullOrEmpty(actualValue) 

      21:         || String.IsNullOrEmpty(expectedValue) 

      22:         || !String.Equals(actualValue, expectedValue, 

      23:                 StringComparison.OrdinalIgnoreCase))             

      24:     {                 

      25:         filterContext.Controller.ViewData.ModelState

      26:             .AddModelError(Field, ErrorMessage);                 

      27:         return;             

      28:     }         

      29: }

Now I can use the CaptchaValidationAttribute like this:

       1: [CaptchaValidationAttribute()]

       2: public ActionResult Register(FormCollection form)         

       3: {

       4:     // INCREDIBLY OVER-SIMPLIFIED BUT YOU GET THE IDEA             

       5:     if (!ViewData.ModelState.IsValid)             

       6:     {             

       7:     return View();

       8:     }         

       9: }

Print | posted on Tuesday, October 28, 2008 5:53 PM | Filed Under [ ASP.NET ]

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