Getting Started with the Captcha
This tutorial explains how to set up a basic Telerik UI for ASP.NET MVC Captcha and highlights the major steps in the configuration of the component.
You will initialize a Captcha and learn how to add audio reading support. Then, you will see how to attach an event handler to the component.
Prerequisites
To successfully complete the tutorial, you need a project that is already configured to use the Telerik UI for ASP.NET MVC components:
To create a new pre-configured project for the Telerik UI for ASP.NET MVC components, you can use a project template.
To manually configure an existing project by using NuGet, see the Adding Telerik UI through NuGet.
1. Prepare the CSHTML File
The first step is to add the required directives at the top of the .cshtml document:
-
To use the Telerik UI for ASP.NET MVC HtmlHelpers:
@using Kendo.Mvc.UI
Optionally, you can structure the document by adding the desired HTML elements like headings, divs, paragraphs, and others.
@using Kendo.Mvc.UI
<h4>Captcha with event handler</h4>
<p>
</p>
2. Initialize the Captcha
Use the Captcha HtmlHelper to add the component to a page:
- The
Name()configuration method is mandatory as its value is used for theidand thenameattributes of the Captcha element. - The
DataCaptchaField()represents the main field. - The
DataCaptchaIdField()represents the ID field. - The
Handler()configuration points to the respective Controller action.
@using Kendo.Mvc.UI
<h4>Captcha with event handler</h4>
<p>
@(Html.Kendo().Captcha()
.Name("captcha")
.DataCaptchaField("Captcha")
.DataCaptchaIdField("CaptchaID")
.Handler(handler => handler.Action("Reset_Events", "captcha"))
)
</p>
3. Add Audio Reader
The next step is to configure the Captcha to allow audio capability. You can do that by using the AudioHandlerFunction() configuration.
@using Kendo.Mvc.UI
<h4>Captcha with event handler</h4>
<script>
function audioHandler(args) {
args.success("../shared/UserFiles/captcha/" + args.data.CaptchaID + ".wav");
}
</script>
<p>
@(Html.Kendo().Captcha()
.Name("captcha")
.DataCaptchaField("Captcha")
.DataCaptchaIdField("CaptchaID")
.Handler(handler => handler.Action("Reset_Events", "captcha"))
.AudioHandlerFunction("audioHandler")
)
</p>
4. Handle a Captcha Event
The Captcha exposes a Change() event that you can handle and assign specific functions to the component. In this tutorial, you will use the Change() event to display a message when the user changes the input value.
@using Kendo.Mvc.UI
<h4>Captcha with event handler</h4>
<script>
function audioHandler(args) {
args.success("../shared/UserFiles/captcha/" + args.data.CaptchaID + ".wav");
}
function onChange(e) {
var value = e.sender.value();
console.log(value);
}
</script>
<p>
@(Html.Kendo().Captcha()
.Name("captcha")
.DataCaptchaField("Captcha")
.DataCaptchaIdField("CaptchaID")
.Handler(handler => handler.Action("Reset_Events", "captcha"))
.AudioHandlerFunction("audioHandler")
.Events(e => e.Change("onChange"))
)
</p>
For more examples, refer to the demo on using the events of the Captcha.
5. (Optional) Reference Existing Captcha Instances
You can reference the Captcha instances that you have created and build on top of their existing configuration:
-
Use the
idattribute of the component instance to establish a reference.<script> var captchaReference = $("#captcha").data("kendoCaptcha"); // captchaReference is a reference to the existing captcha instance of the helper. </script> -
Use the Captcha client-side API to control the behavior of the widget. In this example, you will use the
resetmethod to refresh the captcha.<script> var captchaReference = $("#captcha").data("kendoCaptcha"); // captchaReference is a reference to the existing timeCaptcha instance of the helper. captchaReference.reset(); // refreshes the Captcha </script>
For more information on referencing specific helper instances, see the Methods and Events article.