As a web development best practice, your Web page must validate any value that a user enters on the page. Consider the following options when adding validation:
Validation performed by an HTML5 browser - This validation is performed by the browser before any other form of validation occurs. Refer to Validation Performed by HTML5-Compatible Browsers for more information.
Validation performed by ePortal-generated code in the code-behind file - This validation is performed last, by ePortal. Refer to Validation Performed by ePortal for more information.
Validation performed by ASP.Net validation controls - This validation occurs between the other two methods. Use this form of validation if the two methods above are insufficient. Refer to Adding Validation to Your Web Forms Page for more information.