The Situation: You have a CheckBoxList with an "Other (please specify)" option at the end. If the visitor selects "Other", you want to require that they fill out the "Other" textbox as shown here: You will need to use a Custom Validator attached to the “Other” text box. ASPX file: Client Validation The client validation … Continue reading How to Require a Textbox Be Completed When “Other” is Selected in a CheckBoxList