private void Button_Click(object sender, RoutedEventArgs e) { int check = 0; if (isEmail(username.Text) == false) { MessageBox.Show("Email is not correct!"); } else if (userpass.Password.Trim().Length == 0) { MessageBox.Show("Write a password!"); } else { for (int i = 0; i < userList.Count; i++) { if (username.Text == userList[i].username) { if (userpass.Password == userList[i].password) { userID = userList[i].ID_user; loginpanel.Visibility = Visibility.Collapsed; tabPanel.Visibility = Visibility.Visible; check = 1; ServiceReference1.Service1Client client = new ServiceReference1.Service1Client(); client.getSnakeScoreDataAsync(userID); client.getSnakeScoreDataCompleted += client_getSnakeScoreDataCompleted; } } } if (check == 0) { MessageBox.Show("Incorrect password or username!"); } } }