I'm just getting started with M-V-VM and WPF and having issues understanding some binding issues.
I have a login page that has a ComboBox
and a PasswordBox
. The ComboBox
looks like this:
<ComboBox Name="comboBox1" SelectedItem="{Binding Path=Username}">
This works just fine - my values get updated everytime the SelectedItem
changes on the ComboBox
!
In my ViewModel I have an ICommand
which uses this method to determine if the Login button is active:
public bool CanLogin()
{
return !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password);
}
So my problem is I don't have the PasswordBox
bound to the Password property on the ViewModel - so I have no way to tell when it is updated.
So how do I get the value of the PasswordBox
to my ViewModel? Everything I've read just says don't bind a PasswordBox
for security reasons. I would simply take off the password restriction on the CanLogin() but I need the value to pass along to an AccountService.
I posted a GIST here that is a bindable password box.
Interesting.
look at this blog post and see if it is helping you. http://blog.functionalfun.net/2008/06/wpf-passwordbox-and-data-binding.html
Apparently the link is dead now so here is the original solution (found here):
You can use attached properties to create a helper like this:
public static class PasswordHelper { public static readonly DependencyProperty PasswordProperty = DependencyProperty.RegisterAttached("Password", typeof(string), typeof(PasswordHelper), new FrameworkPropertyMetadata(string.Empty, OnPasswordPropertyChanged)); public static readonly DependencyProperty AttachProperty = DependencyProperty.RegisterAttached("Attach", typeof(bool), typeof(PasswordHelper), new PropertyMetadata(false, Attach)); private static readonly DependencyProperty IsUpdatingProperty = DependencyProperty.RegisterAttached("IsUpdating", typeof(bool), typeof(PasswordHelper)); public static void SetAttach(DependencyObject dp, bool value) { dp.SetValue(AttachProperty, value); } public static bool GetAttach(DependencyObject dp) { return (bool)dp.GetValue(AttachProperty); } public static string GetPassword(DependencyObject dp) { return (string)dp.GetValue(PasswordProperty); } public static void SetPassword(DependencyObject dp, string value) { dp.SetValue(PasswordProperty, value); } private static bool GetIsUpdating(DependencyObject dp) { return (bool)dp.GetValue(IsUpdatingProperty); } private static void SetIsUpdating(DependencyObject dp, bool value) { dp.SetValue(IsUpdatingProperty, value); } private static void OnPasswordPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e) { PasswordBox passwordBox = sender as PasswordBox; passwordBox.PasswordChanged -= PasswordChanged; if (!(bool)GetIsUpdating(passwordBox)) { passwordBox.Password = (string)e.NewValue; } passwordBox.PasswordChanged += PasswordChanged; } private static void Attach(DependencyObject sender, DependencyPropertyChangedEventArgs e) { PasswordBox passwordBox = sender as PasswordBox; if (passwordBox == null) return; if ((bool)e.OldValue) { passwordBox.PasswordChanged -= PasswordChanged; } if ((bool)e.NewValue) { passwordBox.PasswordChanged += PasswordChanged; } } private static void PasswordChanged(object sender, RoutedEventArgs e) { PasswordBox passwordBox = sender as PasswordBox; SetIsUpdating(passwordBox, true); SetPassword(passwordBox, passwordBox.Password); SetIsUpdating(passwordBox, false); } }
Use it:
<PasswordBox w:PasswordHelper.Attach="True"
w:PasswordHelper.Password="{Binding Text, ElementName=plain, Mode=TwoWay}"
Width="100"/>
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