Validation in ASP.NET

Question

What's the best way to validate controls, client-side JavaScript validation or server-side validation?

Answer 1

As others have said, you should do both. Here's why:

Client Side

You want to validate input on the client side first because you can give better feedback to the average user. For example, if they enter an invalid email address and move to the next field, you can show an error message immediately. That way the user can correct every field before they submit the form.

If you only validate on the server, they have to submit the form, get an error message, and try to hunt down the problem.

Server Side

You want to validate on the server side because you can protect against the malicious user, who will probably know how to bypass your JavaScript and submit dangerous input to the server. The server should never trust input from the user, no matter what validation you've tried to do on the client side.

Server side validation is also important for compatibility - not all users will have JavaScript enabled.

Source JavaScript ClientSide vs. ServerSide Validation