Check if primary key exists

Hi!

I have created a formview which I among other things uses to insert new values into a database. What I want to check is if the primary key which is put into the form already exists in the db. If it is I want to get a message to my web page, if not the data can be inserted.

How can I do this?

And if the only way to control this is to create a stored procedure. How do I write such a proc?

If you attempt to insert a duplicate value into a PK field, an exception will be thrown. Why not set it to auto-increment and avoid all of this?

HTH,
Ryan