Validate Captcha by arithmetic operation.

[Berkman]

Hi,

I have the following scenario to be achieved. I want to display a captcha in numeric form and want the user to perform an arithmetic calculation and enter the result in captcha textbox and hence perform a validation. Is this possible using RadCaptcha?

Please help,
Berk.

[Princy]

Hello Berk,

Yes, it is possible to achieve your scenario. Please have a look at the following code in which captcha validation is done based on the sum of numbers.

ASPX:

<telerik:RadCaptcha ID="RadCaptcha1" runat="server" ValidationGroup="CaptchaValidation" ErrorMessage="Page not valid. The code you entered is not valid."
    CaptchaTextBoxCssClass="textBox" OnCaptchaValidate="RadCaptcha1_CaptchaValidate">
    <CaptchaImage ImageCssClass="imageClass" BackgroundColor="#dff3ff" TextColor="Black"
        RenderImageOnly="true" />
</telerik:RadCaptcha>
Enter the sum of the digits in the validation code <br />(enter 0 if there are not any):<br />
<asp:TextBox ID="ValdiationCodeDigitsSum" runat="server" />
<asp:Button ID="btnValidate" runat="server" Text="Verify Code" ValidationGroup="CaptchaValidation" />

C#:

private string oldCaptchaCode;

protected void Page_Init(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        Session["CaptchaCode"] = RadCaptcha1.CaptchaImage.Text;
    }
}

protected void RadCaptcha1_CaptchaValidate(object sender, CaptchaValidateEventArgs e)
{
    e.CancelDefaultValidation = true;
    string validationCodeNumbers = Regex.Replace(Session["CaptchaCode"].ToString(), "[^0-9]", "");
    int digitsSum = 0;
    foreach (char c in validationCodeNumbers)
    {
        digitsSum += Convert.ToInt32(c.ToString());
    }

    int enteredDigitsSum = 0;
    e.IsValid = Int32.TryParse(ValdiationCodeDigitsSum.Text, out enteredDigitsSum) && digitsSum == enteredDigitsSum;
    if (e.IsValid)
    {
        RadCaptcha1.CaptchaImage.ImageCssClass = "imgCorrectCode";
    }
    else
    {
        RadCaptcha1.CaptchaImage.ImageCssClass = "imgWrongCode";
    }
    Session["CaptchaCode"] = RadCaptcha1.CaptchaImage.Text;
}

Thanks,
Princy.