I am new for C#. i am developing web application using C#,asp.net and my database sql server 2005.
my table has for column:
firstname,lastname,username ,email
username and email must be unique with in the table.
now
i have a registration form:
firstname:
lastname:
username:
email:


now i want to check username and email if they already registered... so that if username or and email are already registered, i want to show a message on label username or and email are taken, try with other username or and email.

notice.. i know how to add/insert data into my table without checking the value on table, but i could not how can i check the value of the textbox against the value on my table .
your help please