You do realise how dangerous that is, don't you?
Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.
The original problem is probably that you need to change your connection string:
AttachDbFilename=~\App_Data\SAFA.mdf
May be the problem. Try changing it to use Server.MapPath to change teh "~" into a "normal" file path specification.
But seriously, use parametrized queries - a four character sequence typed in the textbox will destroy your entire database table!