Uniqueness on multiple columns - update query

Question

I have made unique keys for four columns in sql server -

 

I want that I want to check this uniqueness in asp.net c# (front-end)...

 

I want to know which approach is better - back-end keys or front-end checking ??

 

Because, the record gets updated ..

 

Eg - I select a record from Gridview , and make the EmployeeID, SubjectID, same - still - instead of giving error, it gets updated.

 

How to stop the updation at this point ?

 

Please guide and help !

 

 

Also, I received a reply -

 

Hi ,

if you have to check the uniqueness of more then a column so you should have to check from back end with stored procedure, Proc make it fast to check

 

Please guide further... Please help