private void email_txb_Leave(object sender, EventArgs e) { if (string.IsNullOrEmpty(email_txb.Text) == true) { e4.SetError(this.email_txb, "Enter an email"); } else if (Regex.IsMatch(email_txb.Text, patt) == false) { e4.SetError(this.email_txb, "Email is Not valid"); } else if (rs.IsemailAva(email_txb.Text) == 1) { e4.SetError(this.email_txb, "Email is Allready registered"); } else { e4.Clear(); } }