你可以用附加属性来做，看到了吗。PasswordBox with MVVM

如果你想把它组合在一个控件和一个命令中

<PasswordBox Name="PasswordBoxPin" PasswordChar="*">
    <PasswordBox.InputBindings>
        <KeyBinding Key="Return" Command="{Binding AuthentifyEmpCommand}" CommandParameter="{Binding ElementName=PasswordBoxPin}"/>
    </PasswordBox.InputBindings>
</PasswordBox>

在你的Vm上(就像Konamiman展示的那样)

public void AuthentifyEmp(object obj)
{
    var passwordBox = obj as PasswordBox;
    var password = passwordBox.Password;
}
private RelayCommand _authentifyEmpCommand;
public RelayCommand AuthentifyEmpCommand => _authentifyEmpCommand ?? (_authentifyEmpCommand = new RelayCommand(AuthentifyEmp, null));

编辑:根据评论，我觉得有必要指出这违反了MVVM模式，只有当这不是您主要关注的问题之一时才使用它。

为了在不破坏MVVM的情况下解决OP问题，我将使用自定义值转换器和必须从密码框中检索的值(密码)的包装器。

public interface IWrappedParameter<T>
{
    T Value { get; }
}

public class PasswordBoxWrapper : IWrappedParameter<string>
{
    private readonly PasswordBox _source;

    public string Value
    {
        get { return _source != null ? _source.Password : string.Empty; }
    }

    public PasswordBoxWrapper(PasswordBox source)
    {
        _source = source;
    }
}

public class PasswordBoxConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        // Implement type and value check here...
        return new PasswordBoxWrapper((PasswordBox)value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new InvalidOperationException("No conversion.");
    }
}

在视图模型中:

public string Username { get; set; }

public ICommand LoginCommand
{
    get
    {
        return new RelayCommand<IWrappedParameter<string>>(password => { Login(Username, password); });
    }
}

private void Login(string username, string password)
{
    // Perform login here...
}

因为视图模型使用IWrappedParameter<T>，所以它不需要任何关于PasswordBoxWrapper或PasswordBoxConverter的知识。这样您就可以将PasswordBox对象与视图模型隔离开来，并且不会破坏MVVM模式。

在视图中:

<Window.Resources>
    <h:PasswordBoxConverter x:Key="PwdConverter" />
</Window.Resources>
...
<PasswordBox Name="PwdBox" />
<Button Content="Login" Command="{Binding LoginCommand}"
        CommandParameter="{Binding ElementName=PwdBox, Converter={StaticResource PwdConverter}}" />

这对我来说很好。

<Button Command="{Binding Connect}" 
        CommandParameter="{Binding ElementName=MyPasswordBox}"/>

虽然我同意避免将密码存储在任何地方很重要，但我仍然需要能够在没有视图的情况下实例化视图模型，并针对它执行测试。

对我来说，有效的解决方案是注册PasswordBox。Password函数，并让视图模型在执行登录代码时调用它。

这意味着视图隐藏代码中的一行代码。

在我的Login中。xaml我有

<PasswordBox x:Name="PasswordBox"/>

在Login.xaml.cs中

LoginViewModel.PasswordHandler = () => PasswordBox.Password;

然后在LoginViewModel.cs我有PasswordHandler定义

public Func<string> PasswordHandler { get; set; }

当需要登录时，代码调用处理程序从视图中获取密码…

bool loginResult = Login(Username, PasswordHandler());

这样，当我想要测试视图模型时，我可以简单地将PasswordHandler设置为一个匿名方法，让我在测试中交付我想要使用的任何密码。

对我来说，这两件事都不对:

实现明文密码属性 将PasswordBox作为命令参数发送给ViewModel

像Steve在CO中描述的那样传输SecurePassword (SecureString实例)似乎是可以接受的。我更喜欢行为而不是背后的代码，而且我还需要能够从视图模型重置密码。

Xaml (Password是ViewModel属性):

<PasswordBox>
    <i:Interaction.Behaviors>
        <behaviors:PasswordBinding BoundPassword="{Binding Password, Mode=TwoWay}" />
    </i:Interaction.Behaviors>
</PasswordBox>

行为:

using System.Security;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;

namespace Evidence.OutlookIntegration.AddinLogic.Behaviors
{
    /// <summary>
    /// Intermediate class that handles password box binding (which is not possible directly).
    /// </summary>
    public class PasswordBoxBindingBehavior : Behavior<PasswordBox>
    {
        // BoundPassword
        public SecureString BoundPassword { get { return (SecureString)GetValue(BoundPasswordProperty); } set { SetValue(BoundPasswordProperty, value); } }
        public static readonly DependencyProperty BoundPasswordProperty = DependencyProperty.Register("BoundPassword", typeof(SecureString), typeof(PasswordBoxBindingBehavior), new FrameworkPropertyMetadata(OnBoundPasswordChanged));

        protected override void OnAttached()
        {
            this.AssociatedObject.PasswordChanged += AssociatedObjectOnPasswordChanged;
            base.OnAttached();
        }

        /// <summary>
        /// Link up the intermediate SecureString (BoundPassword) to the UI instance
        /// </summary>
        private void AssociatedObjectOnPasswordChanged(object s, RoutedEventArgs e)
        {
            this.BoundPassword = this.AssociatedObject.SecurePassword;
        }

        /// <summary>
        /// Reacts to password reset on viewmodel (ViewModel.Password = new SecureString())
        /// </summary>
        private static void OnBoundPasswordChanged(object s, DependencyPropertyChangedEventArgs e)
        {
            var box = ((PasswordBoxBindingBehavior)s).AssociatedObject;
            if (box != null)
            {
                if (((SecureString)e.NewValue).Length == 0)
                    box.Password = string.Empty;
            }
        }

    }
}