command objects use parameters for passing values
to sql statements for type cheking,validation,guarding
against SQL injection attacks,etc.so its a good practice
to use command parameters to sql statements.

when you build a software make sure that you built it by object oriented way
and you organized your files in folders as following way -

if you want to prevent running multiple instance
of the same c# application then check the
following lines.It's sometime necessary to prevent
running multiple instances of the same application.

you can put application specific settings in the
appSettings section of your app.config file in your
c# windows form application.you can access,edit,update
those settings.I show you how -

namespaces is a old concept in c# programming.both
java and c# uses this concept.a namespace is act like
a 'wrapper' around one or many elements which gives
them uniqueness.