How can I capture and prevent user from enter special charaters like *, @, and comma in KeyDown event?

What I have below is not working currently.  It doesn't capture the '*' char.  Also, how can I capture comma(,) and period(.)?  Thank you.
        private void txtContextName_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Decimal || e.KeyCode == (Keys.Shift & Keys.D8) ||
                e.KeyCode == (Keys.Shift & Keys.D1))
                e.Handled = true;
            //e.KeyCode == Keys. '@', '.', ',', '!','*' }
        }