How to bind to a PasswordBox in MVVM

Question

I have come across a problem with binding to a PasswordBox. It seems it's a security risk but I am using the MVVM pattern so I wish to bypass this. I found some interesting code here (has anyone used this or something similar?)

http://www.wpftutorial.net/PasswordBox.html

It technically looks great, but I am unsure of how to retrieve the password.

I basically have properties in my LoginViewModel for Username and Password. Username is fine and is working as it's a TextBox.

I used the code above as stated and entered this

<PasswordBox ff:PasswordHelper.Attach="True"
    ff:PasswordHelper.Password="{Binding Path=Password}" Width="130"/>

When I had the PasswordBox as a TextBox and Binding Path=Password then the property in my LoginViewModel was updated.

My code is very simple, basically I have a Command for my Button. When I press it CanLogin is called and if it returns true it calls Login.
You can see I check my property for Username here which works great.

In Login I send along to my service a Username and Password, Username contains data from my View but Password is Null|Empty

private DelegateCommand loginCommand;

public string Username { get; set; }
public string Password { get; set; }


public ICommand LoginCommand
{
    get
    {
        if (loginCommand == null)
        {
            loginCommand = new DelegateCommand(
                Login, CanLogin );
        }
        return loginCommand;
    }
}

private bool CanLogin()
{
    return !string.IsNullOrEmpty(Username);
}

private void Login()
{
    bool result = securityService.IsValidLogin(Username, Password);

    if (result) { }
    else { }
}

---

This is what I am doing

<TextBox Text="{Binding Path=Username, UpdateSourceTrigger=PropertyChanged}"
         MinWidth="180" />

<PasswordBox ff:PasswordHelper.Attach="True" 
             ff:PasswordHelper.Password="{Binding Path=Password}" Width="130"/>

I have my TextBox, this is no problem, but in my ViewModel the Password is empty.

Am I doing something wrong or missing a step?

I put a breakpoint and sure enough the code enter the static helper class but it never updates my Password in my ViewModel.

Answer 1

My 2 cents:

I developed once a typical login dialog (user and password boxes, plus "Ok" button) using WPF and MVVM. I solved the password binding issue by simply passing the PasswordBox control itself as a parameter to the command attached to the "Ok" button. So in the view I had:

<PasswordBox Name="txtPassword" VerticalAlignment="Top" Width="120" />
<Button Content="Ok" Command="{Binding Path=OkCommand}"
   CommandParameter="{Binding ElementName=txtPassword}"/>

And in the ViewModel, the Execute method of the attached command was as follows:

void Execute(object parameter)
{
    var passwordBox = parameter as PasswordBox;
    var password = passwordBox.Password;
    //Now go ahead and check the user name and password
}

This slightly violates the MVVM pattern since now the ViewModel knows something about how the View is implemented, but in that particular project I could afford it. Hope it is useful for someone as well.