Silverlight and LINQ-to-SQL

Hi all..

I need help in Silverlight and LINQ-To-SQL.

My requirement is - I have a registration page.

On this Page, I want email and mobile validations - Proper email and 10-digit mobile number.

And, before entering in the database, I need to check that the user-entered email id exists in the database or not.

If it does, then an error message is to be given, else enter the details.

All this is to be done using LINQ-to-SQL in silverlight application.

Please help...

Thanks all in advance !!