C#/WPF：这个回调我错过了什么？

Question

I'm creating a WPF app and i want objects to show up in a listbox, but i'm missing something with the callback: b.CreateGuest() . What should be in the parameters?

Main:

 public partial class MainWindow : Window
{
    bool isBarOpen = false;

    public MainWindow()
    {
        InitializeComponent();

        BouncerListBox.DisplayMemberPath = "name";
    }

    private void CloseButton_Click(object sender, RoutedEventArgs e)
    {
        isBarOpen = false;
    }

    private void OpenButton_Click(object sender, RoutedEventArgs e)
    {
        isBarOpen = true;
        if (isBarOpen == true)
        {
            Bouncer b = new Bouncer();
            BouncerListBox.Items.Insert(0, b.CreateGuest());

        }

    }
}

Bouncer class:

   public class Bouncer
{
    public void CreateGuest(Action <string> callback)
    {
        List<string> guests = new List<string>();
        //long list of names here

        Random rTime = new Random();
        int randomTimePosition = rTime.Next(3, 10) * 1000;
        Thread.Sleep(randomTimePosition);
        Random rGuest = new Random();
        int randomGuestPosition = rGuest.Next(guests.Count);
        string randomName = guests[randomGuestPosition];

        var patron = new Patron();
        patron.Name = randomName;

        callback($" The bouncer lets in {patron.Name} into the bar.");

    }
}

The patron class just have a property with get set name.

Answer 1

When you are calling b.CreateGuest() you are not passing a callback

to do this with a callback (note this is not the best approach)

CreateGuest(msg => BouncerListBox.Items.Insert(0, msg ) );

better would be to just have

return " The bouncer lets in {patron.Name} into the bar."; 

at the end of CreateGuest() then your original code would work

or you could try an mvvm aproach and create a message list on the bar using ObservableCollection<string> then bind that to the listbox's itemSource then just add your message to the bars message list

the rest of your code is truly awful though with useless variables being created to no purpose

cleaned up your code should look something like this

Window (no added code behind)

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        >
    <Window.DataContext>
        <local:Bar/>
    </Window.DataContext>
    <StackPanel>
        <ToggleButton IsChecked="{Binding IsOpen}">Is Open</ToggleButton>
        <ListBox ItemsSource="{Binding Guests}" DisplayMemberPath="Name"/>
        <Button Command="{Binding Bouncer.AllowGuestAccess, Mode=OneWay}">Allow guest in</Button>
        <ListBox ItemsSource="{Binding Message}"/>

    </StackPanel>
</Window>

your object model (using prism)

public class Bar :BindableBase
{
    public Bar()
    {
        Bouncer = new Bouncer() { Bar = this };
    }

    private bool _IsOpen;

    public bool IsOpen
    {
        get => _IsOpen;
        set => SetProperty(ref _IsOpen, value,()=>Bouncer.AllowGuestAccess.RaiseCanExecuteChanged());
    }
    public Bouncer Bouncer { get;  }
    public ObservableCollection<string> Message { get; } = new ObservableCollection<string>();
    public ObservableCollection<Patron> Guests { get; } = new ObservableCollection<Patron>();
}

public class Bouncer
{
    public Bouncer()
    {
        AllowGuestAccess = new DelegateCommand(() =>
        {
            var patron = new Patron();
            Bar.Guests.Add(patron);
            Bar.Message.Insert(0, $"{patron.Name} has been admitted");
        },()=>Bar.IsOpen);
    }
    public Bar Bar { get; set; }

    public DelegateCommand AllowGuestAccess { get; }
}
public class Patron
{
    public static Random Rnd { get; } = new Random();
    public static List<string> Names { get; } = new List<string>();

    public Patron()
    {
        Name = Names[Rnd.Next(Names.Count)];
    }

    public string Name { get; }
}

Answer 2

BouncerListBox.Items.Insert(0, b.CreateGuest( status => {
  // do something with status here...
}));

But b.CreateGuest() should return an Object, which is what BouncerListBox.Items.Insert(0, b.CreateGuest()); expect.

May you code should be

public string CreateGuest()
{

    List<string> guests = new List<string>();
    //long list of names here

    Random rTime = new Random();
    int randomTimePosition = rTime.Next(3, 10) * 1000;
    Thread.Sleep(randomTimePosition);
    Random rGuest = new Random();
    int randomGuestPosition = rGuest.Next(guests.Count);
    string randomName = guests[randomGuestPosition];

    var patron = new Patron();
    patron.Name = randomName;

    return $" The bouncer lets in {patron.Name} into the bar.";
}