Login Wpf ...is it right?

Question

Hi, i have a WPF Application with a LoginWindow to access,so i create a Splash Screen for this Login window as follow :

- in App.xaml

< Application x:Class="WPF.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Startup="Application_Startup"
    />

-in App.xaml.cs:

      private void Application_Startup(object sender, StartupEventArgs e)
  {
         Login login = new Login();
        login.Show();
  }

-and in Login.xaml.cs if the log in is succesful :

PrimaryWindow mainWindow= new PrimaryWindow ();

Application.Current.MainWindow = mainWindow;

this.Close();

mainWindow.Show();

.This code is right but sincerely with my poor knowledge i don't know that's a good method to apply for a Login Window or not and i don't know if this method can be "dangerous" for my application that store data from a database and has many features , so i ask you if my way is good or not and if you have a better way can you suggest or show me that?

Thanks for your attention.

Have a lucky day.

Answer 1

Personally, I don't think it's a good idea for a Login window to kill off the main application window. Why not do something like this?

PrimaryWindow mainWindow= new PrimaryWindow ();

Application.Current.MainWindow.Hide(); // or something, don't know the exact syntax

mainWindow.Closed += delegate{Application.Current.MainWindow.Show(); };

mainWindow.Show();

Answer 2

Looks fine to me - this code by itself isn't 'dangerous'. What might be dangerous is how you collect and process the user's credentials in your login window, but you haven't posted that code so I can't comment.

You could optimize this code a little by using StartupUri="Login.xaml" in your Application tag instead of pointing to an event handler, it would achieve the same effect with less code.

Answer 3

Your code seems ok, but personally I like to have things in one place - the login should worry just about login, not whether to show main screen or shutdown application. So, my solution would be something like this:

App.xaml

<Application 
    .... 
    StartupUri="Forms/MainWindow.xaml" >
....
</Application

App.xaml.cs

protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        //Without the next line your app would've ended upon closing Login window:
        ShutdownMode = ShutdownMode.OnExplicitShutdown;
        //Authenticate user (if canceled returns 'false')
        LoginScreen wndLogin = new LoginScreen();
        if (wndLogin.ShowDialog() == false)
        {
            Shutdown();
        }
        else
        {
            //if you have some cache to load, then show some progress dialog,
            //or welcome screen, or whatever...
            //after this, the MainWindow executes, so restore the ShutdownMode,
            //so the app ends with closing of main window (otherwise, you have to call
            //Applicaiton.Current.Shutdown(); explicitly in Closed event of MainWindow)
            ShutdownMode = ShutdownMode.OnMainWindowClose;
        }
    }

Hope this helps.

Answer 4

I would handle this with 2 windows and an Application_Startup method. Here is what my app (which has a similar login idea) looks like:

/// In App.xaml.cs
/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application {
    private MainWindow main = new MainWindow();
    private LoginWindow login = new LoginWindow();

    private void Application_Startup(object sender, StartupEventArgs e) {
        Application.Current.ShutdownMode = ShutdownMode.OnMainWindowClose;
        Application.Current.MainWindow = login;

        login.LoginSuccessful += main.StartupMainWindow;
        login.Show();
    }
}

/// In LoginWindow.xaml.cs
/// <summary>
/// Interaction logic for LoginWindow.xaml
/// </summary>
public partial class LoginWindow : Window {
    internal event EventHandler LoginSuccessful;

    public LoginWindow() { InitializeComponent(); }

    private void logInButton_Click(object sender, RoutedEventArgs e) {
        if ( // Appropriate Login Check Here) {
            LoginSuccessful(this, null);
            Close();
        } else {
            // Alert the user that login failed
        }
    }
}

/// In MainWindow.xaml.cs
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window {
    public MainWindow() { InitializeComponent(); }

    internal void StartupMainWindow(object sender, EventArgs e) {
        Application.Current.MainWindow = this;
        Show();
    }
}

This allows the user to close the application simply by closing the login window (i.e. not logging in at all) or by closing the main window AFTER they have used it for a while.

Answer 5

I usually use a Service Object to handle anything related to login. I also have a Session and Credentials objects (custom made) that is persisted through the program. All the login logic is stored inside the SessionService.

static void Main(string[] args)
{
    ServiceManager.RegisterService<SessionService>();

    Session session;
    if(ServiceManager.GetService<SessionService>().CreateSession(out session) == CreateSessionResult.Success)
    {
        MainWindow window = new MainWindow();
        window.SetSession(session);
        Application.Run(window);
    }
    ServiceManager.UnregisterService<SessionService>();
}