<Captcha>

The Captcha tag renders a CAPTCHA challenge — an image of distorted characters the user must read and type — to help confirm the user is human. If your forms are public, web bots will eventually find them and submit junk; a CAPTCHA reduces the frequency of those submissions.

NOTE

Due to a limitation in the underlying DNN CAPTCHA control, this tag can only be used in the FormView module.

Example

<AddForm>
  ...
  <table>
    <tr>
      <td>
        <Label For="txtFirstName" Text="First Name" />
        <Textbox id="txtFirstName" DataField="FirstName" DataType="string" />
      </td>
    </tr>
    <tr>
      <td>
        <Label For="txtLastName" Text="Last Name" />
        <Textbox Id="txtLastName" DataField="LastName" DataType="string" />
       </td>
    </tr>
    <tr>
      <td>
        <Captcha CaptchaLength="5" />
      </td>
    </tr>
    <tr>
      <td colspan="2">
        <AddButton Text="Add"/>&nbsp; <CancelButton Text="Cancel"/>
      </td>
    </tr>
  </table>
</AddForm>

Properties

Property	Values	Default	Description
ID *	string		Unique identifier for the control within the form
AccessKey	string		Keyboard shortcut character (e.g. F for Alt+F)
BackgroundColor	color name | #dddddd		Background color used behind the CAPTCHA characters
BackgroundImage	URL		URL to an image file used as the background behind the characters
CaptchaChars	string	abc...XYZ23456789	Character set used to generate the challenge text
CaptchaHeight	size	100px	Height of the CAPTCHA image
CaptchaLength	integer	6	Number of characters in the challenge
CaptchaWidth	size	300px	Width of the CAPTCHA image
CssClass	string		CSS class name(s) for styling the control
Enabled	True False	True	When False, the control is disabled (grayed out and not interactive)
ErrorMessage	string	(localized)	Message shown to the user if their input does not match the challenge
ErrorStyle	style attributes		Styling for the error message — uses ASP.NET nested style syntax (e.g. ErrorStyle-ForeColor="red")
Expiration	integer (seconds)	120	How long the challenge remains valid before it must be regenerated
Height	size		Height of the control
Style	string		Inline CSS (e.g. color: red; border: solid 1px black;)
TabIndex	integer		Tab order for keyboard navigation
Text	string	(localized)	Caption displayed next to the CAPTCHA image (e.g. "Enter the code shown above")
ToolTip	string		Text displayed on mouse hover
Visible	True False	True	Shows or hides the control
Width	size		Width of the control

* Required property

Deprecated Properties

These properties use ASP.NET inline styling and are no longer recommended for modern web development. Use the CssClass property to apply CSS classes or the Style property for inline CSS instead.

Property	Values	Description
BackColor	color name | #dddddd	Background color of the control
BorderColor	color name | #dddddd	Border color of the control
BorderStyle	NotSet None Dotted Dashed Solid Double Groove Ridge Inset Outset	Border style of the control
BorderWidth	size	Border width of the control
Font-Bold	True False	Bold text
Font-Italic	True False	Italic text
Font-Names	string	Font family name
Font-Overline	True False	Overline text decoration
Font-Size	XX-Small X-Small Small Medium Large X-Large XX-Large or size	Font size
Font-Strikeout	True False	Strikethrough text decoration
Font-Underline	True False	Underline text decoration
ForeColor	color name | #dddddd	Text color of the control

The ErrorStyle property accepts the same set of nested style attributes (e.g. ErrorStyle-Font-Bold, ErrorStyle-ForeColor). These are likewise deprecated — prefer styling the error message via CSS targeting the rendered error element.

Property Details

• ID: Name, consisting of letters and numbers, beginning with a letter, that uniquely identifies the control within the form.

• CaptchaChars: The pool of characters from which challenge text is randomly drawn. The default set deliberately omits visually ambiguous characters (such as O, 0, I, 1) to reduce user errors. Override this only if you have a specific reason — for example, to limit the challenge to digits or to avoid characters that don't render well in your chosen font.

• ErrorStyle: Styling for the error message displayed when the user's input doesn't match the challenge. Uses ASP.NET nested style syntax: prefix any deprecated style attribute with ErrorStyle- (e.g. ErrorStyle-ForeColor="red", ErrorStyle-Font-Bold="True"). For modern styling, prefer CSS targeting the rendered error element.