Validation - Introduction
Ever since the first dynamic website was created, form validation has been an important subject. Getting user input through the system requires much attention, and with previous serverside scripting languages, there were no standard way of dealing with form validation. For that reason, clientside scripting has been used in many cases, but as you probably know, clientside scripting is not bulletproof - it can easily be bypassed or simply turned off. With ASP.NET, webdevelopers were finally given a good, standard set of tools for validating forms. The validation controls of ASP.NET is based on both clientside and serverside technology, which brings the best from both worlds, to make sure that validating a form is as easy as ever.
ASP.NET 2.0, which is the latest version as I write this, comes with several different validation controls for different purposes. In the following chapters, we will show examples of each of them. They all work in different ways, but essentially they do the same - they make sure that a form field has been properly filled by the user.