Validating the SingleImagePlaceholderControl

The technique for validating a SingleImagePlaceholderControl is similar to that of the HtmlPlaceholderControl. We first need to find a way to read its contents using client-side script. Once we have the content, we can proceed to check to see if it is valid. If it isn’t, we cancel the save.

Let’s build a required SingleImagePlaceholderControl validator. In this example, we will program the validator to verify that the author has uploaded a picture to the control.

Retrieving the Value of the SingleImagePlaceholderControl

The SingleImagePlaceholderControl is rendered on the browser as a series of hidden form fields and images organized neatly within tables.

Here’s a snippet of the generated code:

. . . code continues . . .
<input type="hidden" value="" name="NCPH_ImagePlaceholderDefinitionName"
 placeholderType="singleImage" /><input type="hidden" value="" name="NCPHHRef_
ImagePlaceholderDefinitionName"/>
<input type="hidden" value=""...