private void button1_Click(object sender, EventArgs e)
{
DBFactory factory = new ODBCFactory();
DBAccess dba = new DBAccess(factory);
dba.Open("connectionString");
DataSet ds = dba.ExecSQL("select * from persons.Address");
}
private void button2_Click(object sender, EventArgs e)
{
string conf = ConfigurationManager.AppSettings["DBAccess"].ToString().Trim();
Assembly asm = Assembly.GetExecutingAssembly();
Type t = asm.GetType(conf);
DBFactory factory = (DBFactory) Activator.CreateInstance(t);
DBAccess dba = new DBAccess(factory);
dba.Open("connectionString");
DataSet ds = dba.ExecSQL("select * from persons.Address");
}