Alert message in asp.net from database

Question

I have a user details table in which passport number is primary key and identity number, mobile number and email id are unique keys. It is getting inserted into database while registring. but what my problem is that if the same passportnumber or identity number or email id ro mobile number is registering then i have to mention it in an alertbox so and so passportnumber or email id or identity number or mobile number registered before