private void btn_accountcheck_Click(object sender, EventArgs e) { SqlConnection con = new SqlConnection(SqlLink.linkmethod()); SqlCommand cmd = new SqlCommand(SqlSelect.UserCheckmethod(), con); cmd.Parameters.AddWithValue("@username", tb_account.Text); con.Open(); SqlDataReader dataReader = cmd.ExecuteReader(); DataSet ds = new DataSet(); con.Close(); if (dataReader.Read()) { if (dataReader[0].ToString() == "0") { MessageBox.Show("帳號可以使用"); return; } else { MessageBox.Show("帳號已被使用"); return; } } }