Caliburn.Micro support for PasswordBox?

Question

The Caliburn.Micro home page at http://caliburnmicro.com makes the below claim but I am unable to make CM work with a PasswordBox control using any variation I can think of from that example. Don't see how this would work anyway since the names are not the same case. Does anyone have a CM example that does allow me to get the value of the PasswordBox? Is there a particular version of CM required? I'm running version 1.5.2 of CM. Ideally w/o using Attached Properties but if can work with CM and the only way then fine. Please no lectures on security issues as that is not an issue in my case.

---

Apply methods between your view and view model automatically with parameters and guard methods

<StackPanel>
    <TextBox x:Name="Username" />
    <PasswordBox x:Name="Password" />
    <Button x:Name="Login" Content="Log in" />
</StackPanel>

public bool CanLogin(string username, string password)
{
    return !String.IsNullOrEmpty(username) && !String.IsNullOrEmpty(password);
}

public string Login(string username, string password)
{
    ...
}

Answer 1

Here's a much more simplified example, including a binding convention so that PasswordBox binding in Caliburn.Micro Just Works™:

public static class PasswordBoxHelper
{
    public static readonly DependencyProperty BoundPasswordProperty =
        DependencyProperty.RegisterAttached("BoundPassword",
            typeof(string),
            typeof(PasswordBoxHelper),
            new FrameworkPropertyMetadata(string.Empty, OnBoundPasswordChanged));

    public static string GetBoundPassword(DependencyObject d)
    {
        var box = d as PasswordBox;
        if (box != null)
        {
            // this funny little dance here ensures that we've hooked the
            // PasswordChanged event once, and only once.
            box.PasswordChanged -= PasswordChanged;
            box.PasswordChanged += PasswordChanged;
        }

        return (string)d.GetValue(BoundPasswordProperty);
    }

    public static void SetBoundPassword(DependencyObject d, string value)
    {
        if (string.Equals(value, GetBoundPassword(d)))
            return; // and this is how we prevent infinite recursion

        d.SetValue(BoundPasswordProperty, value);
    }

    private static void OnBoundPasswordChanged(
        DependencyObject d,
        DependencyPropertyChangedEventArgs e)
    {
        var box = d as PasswordBox;

        if (box == null)
            return;

        box.Password = GetBoundPassword(d);
    }

    private static void PasswordChanged(object sender, RoutedEventArgs e)
    {
        PasswordBox password = sender as PasswordBox;

        SetBoundPassword(password, password.Password);

        // set cursor past the last character in the password box
        password.GetType().GetMethod("Select", BindingFlags.Instance | BindingFlags.NonPublic).Invoke(password, new object[] { password.Password.Length, 0 }); 
    }

}

Then, in your bootstrapper:

public sealed class Bootstrapper : BootstrapperBase
{
    public Bootstrapper()
    {
        Initialize();

        ConventionManager.AddElementConvention<PasswordBox>(
            PasswordBoxHelper.BoundPasswordProperty,
            "Password",
            "PasswordChanged");
    }

    // other bootstrapper stuff here
}

Answer 2

The solutions provided here seem to be needlessly complicated.

We can very easily use Caliburn.Micro actions to send our password to the ViewModel.

XAML:

<PasswordBox cal:Message.Attach="[Event PasswordChanged] = [Action OnPasswordChanged($source)]" />

ViewModel:

public void OnPasswordChanged(PasswordBox source)
{
    password = source.Password;
}

Then remember to clear the password fields so they don't remain in memory.

NOTE: Obviously this solution doesn't allow you to easily change the password from the ViewModel, if that is necessary, then it's probably best to go with the attached property approach.

Answer 3

I've only been able to get it to work with dependency properties, effectively bypassing the convention binding goodness that Caliburn.Micro supplies. I recognize that's not your ideal, but pragmatically this is the solution I regularly use. I believe when I hit this snag historically, I found this post on StackOverflow that led me in this direction. For your consideration:

public class BoundPasswordBox
    {
        private static bool _updating = false;

        /// <summary>
        /// BoundPassword Attached Dependency Property
        /// </summary>
        public static readonly DependencyProperty BoundPasswordProperty =
            DependencyProperty.RegisterAttached("BoundPassword",
                typeof(string),
                typeof(BoundPasswordBox),
                new FrameworkPropertyMetadata(string.Empty, OnBoundPasswordChanged));

        /// <summary>
        /// Gets the BoundPassword property.
        /// </summary>
        public static string GetBoundPassword(DependencyObject d)
        {
            return (string)d.GetValue(BoundPasswordProperty);
        }

        /// <summary>
        /// Sets the BoundPassword property.
        /// </summary>
        public static void SetBoundPassword(DependencyObject d, string value)
        {
            d.SetValue(BoundPasswordProperty, value);
        }

        /// <summary>
        /// Handles changes to the BoundPassword property.
        /// </summary>
        private static void OnBoundPasswordChanged(
            DependencyObject d,
            DependencyPropertyChangedEventArgs e)
        {
            PasswordBox password = d as PasswordBox;
            if (password != null)
            {
                // Disconnect the handler while we're updating.
                password.PasswordChanged -= PasswordChanged;
            }

            if (e.NewValue != null)
            {
                if (!_updating)
                {
                    password.Password = e.NewValue.ToString();
                }
            }
            else 
            {
                password.Password = string.Empty;
            }
            // Now, reconnect the handler.
            password.PasswordChanged += PasswordChanged;
        }

        /// <summary>
        /// Handles the password change event.
        /// </summary>
        static void PasswordChanged(object sender, RoutedEventArgs e)
        {
            PasswordBox password = sender as PasswordBox;
            _updating = true;
            SetBoundPassword(password, password.Password);
            _updating = false;
        }
    }

Then, in your XAML:

<PasswordBox pwbx:BoundPasswordBox.BoundPassword="{Binding UserPassword, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged,NotifyOnValidationError=True,ValidatesOnDataErrors=True}" />

and pwbx is found as a namespace on the Window tag:

<Window x:Class="MyProject.Views.LoginView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             xmlns:pwbx="clr-namespace:MyProject.Client.Controls">

The ViewModel:

using Caliburn.Micro;
using MyProject.Core;
using MyProject.Repositories;
using MyProject.Types;
using MyProject.ViewModels.Interfaces;

namespace MyProject.ViewModels
{
    public class LoginViewModel : Screen, ILoginViewModel
    {
        private readonly IWindowManager _windowManager;
        private readonly IUnitRepository _unitRepository;
        public bool IsLoginValid { get; set; }
        public Unit LoggedInUnit { get; set; }

        private string _password;
        public string UserPassword
        {
            get { return _password; }
            set
            {
                _password = value;
                NotifyOfPropertyChange(() => UserPassword);
                NotifyOfPropertyChange(() => CanLogin);
            }
        }

        private string _name;
        public string Username
        {
            get { return _name; }
            set
            {
                _name = value;
                NotifyOfPropertyChange(() => Username);
                NotifyOfPropertyChange(() => CanLogin);
            }
        }
        public LoginViewModel(IWindowManager windowManager,IUnitRepository unitRepository)
        {
            _windowManager = windowManager;
            _unitRepository = unitRepository;
            DisplayName = "MyProject - Login";
            Version = ApplicationVersionRepository.GetVersion();
        }

        public string Version { get; private set; }

        public void Login()
        {
            // Login logic
            var credentials = new UserCredentials { Username = Username, Password=UserPassword };

            var resp = _unitRepository.AuthenticateUnit(credentials);
            if (resp == null) return;
            if (resp.IsValid)
            {
                IsLoginValid = true;
                LoggedInUnit = resp.Unit;
                TryClose();
            }
            else
            {
                var dialog = new MessageBoxViewModel(DialogType.Warning, DialogButton.Ok, "Login Failed", "Login Error: " + resp.InvalidReason);
                _windowManager.ShowDialog(dialog);
            }
        }

        public bool CanLogin
        {
            get
            {
                return !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(UserPassword);
            }
        }
    }
}