Do you use both Client-side and Server-side validation techniques side by side when validating input from a user, e.g. via a contact form?If so, is it really necessary?  Are you over engineering?
Do you use both Client-side and Server-side validation techniques?
web development;validation
Yes, and you should.This maintains instant user feedback without wasted postbacks whilst also guarding against users disabling JavaScript.This is how the ASP.NET Validation Controls work.  It is certainly not over-engineering as using one without the other has drawbacks.