how can i create rules in data base using c#.net and how to use them

I just want to note that you don't need to use c# for this. You can implement your rules through stored procedures. Calls to the database through these procedures would ensure your requirements are met. Create a database account that does not have table-level privileges and allow allow access through those procs. Any .NET language could be used for this.

If you're looking for a pure CLR solution you can also try this walkthrough[^].

Cheers.