WPF：在App.xaml.cs中设置MainWindow，访问其变量

Question

in the past I could access a windows variables as it closes, so like a return parameter. But at the moment having an issue with this. See the code below:

public partial class App : Application
    {
        //Public list of users and form can access
        ObservableCollection<User> LoggedUsers = new ObservableCollection<User>();
        public ObservableCollection<User> Logged
        {
            get
            {
                return LoggedUsers;
            }
        }

        protected override void OnStartup(System.Windows.StartupEventArgs e)
        {
            if (!AreSettingsSet())
            {
                this.MainWindow = new Views.LoginWindow();
                this.MainWindow.ShowDialog(); // Waits until closed.

                //If the login form was closed properly, handle the user
                if (MainWindow.DialogResult == true)
                {
                    //Add the user to the list of logged users
                    User returned = MainWindow.returnUser;
                    LoggedUsers.Add(returned);
                }

                // Recheck the settings now that the login screen has been closed.
                if (!AreSettingsSet())
                {
                    // Tell the user there is a problem and quit.
                    this.Shutdown();
                }
            }

            this.MainWindow = new Views.Main();
            this.MainWindow.Show();
        }

        private bool AreSettingsSet()
        {
            MessageBox.Show(Logged.Count().ToString());
            return false;
        }
    }

This code should open the login window if the AreSettingsSet method returns false (does at the moment for testing). This works fine, i'm having an issue with getting an object back from the Views.LoginWindow() window, here the code:

//Give App access to user object outside of this form
        public User returnUser
        {
            get
            {
                return user;
            }
        }

        //Public user object, start empty
        User user = new User();

Where am I going wrong? How do I get the LoggedUsers object from my login window? At the moment i'm getting an error on the following line.

Code:

User returned = MainWindow.returnUser;

Error:

'System.Windows.Window' does not contain a definition for 'returnUser' and no extension method 'returnUser' accepting a first argument of type 'System.Windows.Window' could be found (are you missing a using directive or an assembly reference?)

Answer 1

The framework stores your LoginWindow as Window .

You can cast the MainWindow to LoginWindow

User returned = ((Views.LoginWindow)MainWindow).returnUser;

Or use the as operator

User returned = (MainWindow as Views.LoginWindow).returnUser;