对于像我这样的新手，这里有一个完整的工作样本。谢谢Konamiman。

XAML

    <PasswordBox x:Name="textBoxPassword"/>
    <Button x:Name="buttonLogin" Content="Login"
            Command="{Binding PasswordCommand}"
            CommandParameter="{Binding ElementName=textBoxPassword}"/> 

ViewModel

public class YourViewModel : ViewModelBase
{
    private ICommand _passwordCommand;
    public ICommand PasswordCommand
    {
        get {
            if (_passwordCommand == null) {
                _passwordCommand = new RelayCommand<object>(PasswordClick);
            }
            return _passwordCommand;
        }
    }

    public YourViewModel()
    {
    }

    private void PasswordClick(object p)
    {
        var password = p as PasswordBox;
        Console.WriteLine("Password is: {0}", password.Password);
    }
}

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}"/>

我使用这种方法并通过密码框，虽然这确实违反了MVVM，这对我来说是必不可少的，因为我正在使用一个内容控件与数据模板为我的登录在我的shell，这是一个复杂的shell环境。因此，访问shell背后的代码将是垃圾。

据我所知，我认为传递密码框与从后面的代码访问控制权是一样的。在这个实现中，我没有视图模型中的密码属性。

按钮命令

Command="{Binding Path=DataContext.LoginCommand, ElementName=MyShell}" CommandParameter="{Binding ElementName=PasswordBox}"

ViewModel

private void Login(object parameter)
{
    System.Windows.Controls.PasswordBox p = (System.Windows.Controls.PasswordBox)parameter;
    MessageBox.Show(p.Password);
}

好吧，我的答案更简单，只是在MVVM模式

在类视图模型中

public string password;

PasswordChangedCommand = new DelegateCommand<RoutedEventArgs>(PasswordChanged);

Private void PasswordChanged(RoutedEventArgs obj)

{

    var e = (WatermarkPasswordBox)obj.OriginalSource;

    //or depending or what are you using

    var e = (PasswordBox)obj.OriginalSource;

    password =e.Password;

}

win提供的PasswordBox或XCeedtoolkit提供的WatermarkPasswordBox的password属性生成一个RoutedEventArgs，以便您可以绑定它。

现在在xmal视图中

<Xceed:WatermarkPasswordBox Watermark="Input your Password" Grid.Column="1" Grid.ColumnSpan="3" Grid.Row="7" PasswordChar="*" >

        <i:Interaction.Triggers>

            <i:EventTrigger EventName="PasswordChanged">

                <prism:InvokeCommandAction Command="{Binding RelativeSource={RelativeSource AncestorType=UserControl}, Path= DataContext.PasswordChangedCommand}" CommandParameter="{Binding RelativeSource={RelativeSource Self}, Path= Password}"/>

            </i:EventTrigger>

        </i:Interaction.Triggers>

    </Xceed:WatermarkPasswordBox>

or

<PasswordBox Grid.Column="1" Grid.ColumnSpan="3" Grid.Row="7" PasswordChar="*" >

        <i:Interaction.Triggers>

            <i:EventTrigger EventName="PasswordChanged">

                <prism:InvokeCommandAction Command="{Binding RelativeSource={RelativeSource AncestorType=UserControl}, Path= DataContext.PasswordChangedCommand}" CommandParameter="{Binding RelativeSource={RelativeSource Self}, Path= Password}"/>

            </i:EventTrigger>

        </i:Interaction.Triggers>

    </PasswordBox>

我在这里发布了一个GIST，它是一个可绑定的密码框。

using System.Windows;
using System.Windows.Controls;

namespace CustomControl
{
    public class BindablePasswordBox : Decorator
    {
        /// <summary>
        /// The password dependency property.
        /// </summary>
        public static readonly DependencyProperty PasswordProperty;

        private bool isPreventCallback;
        private RoutedEventHandler savedCallback;

        /// <summary>
        /// Static constructor to initialize the dependency properties.
        /// </summary>
        static BindablePasswordBox()
        {
            PasswordProperty = DependencyProperty.Register(
                "Password",
                typeof(string),
                typeof(BindablePasswordBox),
                new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, new PropertyChangedCallback(OnPasswordPropertyChanged))
            );
        }

        /// <summary>
        /// Saves the password changed callback and sets the child element to the password box.
        /// </summary>
        public BindablePasswordBox()
        {
            savedCallback = HandlePasswordChanged;

            PasswordBox passwordBox = new PasswordBox();
            passwordBox.PasswordChanged += savedCallback;
            Child = passwordBox;
        }

        /// <summary>
        /// The password dependency property.
        /// </summary>
        public string Password
        {
            get { return GetValue(PasswordProperty) as string; }
            set { SetValue(PasswordProperty, value); }
        }

        /// <summary>
        /// Handles changes to the password dependency property.
        /// </summary>
        /// <param name="d">the dependency object</param>
        /// <param name="eventArgs">the event args</param>
        private static void OnPasswordPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs eventArgs)
        {
            BindablePasswordBox bindablePasswordBox = (BindablePasswordBox) d;
            PasswordBox passwordBox = (PasswordBox) bindablePasswordBox.Child;

            if (bindablePasswordBox.isPreventCallback)
            {
                return;
            }

            passwordBox.PasswordChanged -= bindablePasswordBox.savedCallback;
            passwordBox.Password = (eventArgs.NewValue != null) ? eventArgs.NewValue.ToString() : "";
            passwordBox.PasswordChanged += bindablePasswordBox.savedCallback;
        }

        /// <summary>
        /// Handles the password changed event.
        /// </summary>
        /// <param name="sender">the sender</param>
        /// <param name="eventArgs">the event args</param>
        private void HandlePasswordChanged(object sender, RoutedEventArgs eventArgs)
        {
            PasswordBox passwordBox = (PasswordBox) sender;

            isPreventCallback = true;
            Password = passwordBox.Password;
            isPreventCallback = false;
        }
    }
}