如果验证返回false，则执行javascript以阻止数据进入数据库

I am using asp.net. I want to check the value of certain textboxes before entering their value in database. I tried using javascript. However it gives me an alert on checking the value but the data still gets inserted into database. Is it happening because the javascript I am using is client-side ? What's the solution for this ? I am using asp.net. I want to check the value o