private void Button_Click(object sender, RoutedEventArgs e) { if (email.Text.ToString() != "" || confirmEmail.Text.ToString() != "" || password.Text.ToString() != "" || confirmPassword.Text.ToString() != "") { string inputEmail = email.Text.ToString(); string inputConfrimEmail = confirmEmail.Text.ToString(); string inputPassword = password.Text.ToString(); string inputConfrimPassword = confirmPassword.Text.ToString(); Boolean alreadyExist = true; using (SqlConnection connection = new SqlConnection("Data Source=localhost;Initial Catalog=vidigo;User ID=SYSTEM;Password=school10;")) using (SqlCommand checkOkay = new SqlCommand("Select USERNAME FROM VIGICLIENT WHERE " + email + "=USERNAME", connection)) { connection.Open(); using (SqlDataReader reader = checkOkay.ExecuteReader()) { if (reader.HasRows) { emailAlreadyExist(); alreadyExist = true; } else { alreadyExist = false; } } connection.Close(); } if (!alreadyExist) { billingWindow billingWindow = new billingWindow(inputEmail, inputPassword); billingWindow.Show(); this.Close(); } } }