Webforms C#: Validating FormView fields

Title says it ... my C# web application uses a number of FormViews that are
inserted/updated/deleted via stored procedures.

Is there a way thru C# coding (example?) to validate a date field as valid
input before inserting/updating? Test the length of a varchar/char field?
Validate an int field as valid numeric input (no alpha) ... and so on?

I would like to do this validation before the stored procedures fire
(perhaps stopping), of course so the user does not see the cryptic messages
that come back by default.

It would be nice to see some C# examples or the specifics on another
workarounds. Thanks to all you pros for reading.