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>

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。

使用附加行为和ICommand发送一个SecureString到视图模型

在实现MVVM时，代码隐藏并没有错。MVVM是一种架构模式，旨在将视图与模型/业务逻辑分离。MVVM描述了如何以可重复的方式(模式)实现这一目标。它不关心实现细节，比如如何构造或实现视图。它只是画出边界，并根据这个模式的术语定义什么是视图，视图模型和什么是模型。

MVVM不关心语言(XAML或c#)或编译器(部分类)。独立于语言是设计模式的强制性特征——它必须与语言无关。

However, code-behind has some draw backs like making your UI logic harder to understand, when it is wildly distributed between XAML and C#. But most important implementing UI logic or objects like templates, styles, triggers, animations etc in C# is very complex and ugly/less readable than using XAML. XAML is a markup language that uses tags and nesting to visualize object hierarchy. Creating UI using XAML is very convenient. Although there are situations where you are fine choosing to implement UI logic in C# (or code-behind). Handling the PasswordBox is one example.

因此，在代码背后通过处理PasswordBox来处理PasswordBox。PasswordChanged没有违反MVVM模式。

一个明显的违规是将控件(PasswordBox)传递给视图模型。许多解决方案都推荐这样做，例如，将PasswordBox的实例作为ICommand传递。CommandParameter添加到视图模型。这显然是一个非常糟糕和不必要的建议。

如果你不关心使用c#，只是想保持你的代码文件干净，或者只是想封装一个行为/UI逻辑，你总是可以使用附加属性并实现附加行为。

与臭名昭著的支持绑定纯文本密码的广泛传播帮助器(非常糟糕的反模式和安全风险)相反，此行为使用ICommand将密码作为SecureString发送到视图模型，每当PasswordBox抛出PasswordBox时。PasswordChanged事件。

MainWindow.xaml

<Window>
  <Window.DataContext>
    <ViewModel />
  </Window.DataContext>

  <PasswordBox PasswordBox.Command="{Binding VerifyPasswordCommand}" />
</Window>

ViewModel.cs

public class ViewModel : INotifyPropertyChanged
{
  public ICommand VerifyPasswordCommand => new RelayCommand(VerifyPassword);

  public void VerifyPassword(object commadParameter)
  {
    if (commandParameter is SecureString secureString)
    {
      IntPtr valuePtr = IntPtr.Zero;
      try
      {
        valuePtr = Marshal.SecureStringToGlobalAllocUnicode(value);
        string plainTextPassword = Marshal.PtrToStringUni(valuePtr);

        // Handle plain text password. 
        // It's recommended to convert the SecureString to plain text in the model, when really needed.
      } 
      finally 
      {
        Marshal.ZeroFreeGlobalAllocUnicode(valuePtr);
      }
    }
  }
}

PasswordBox.cs

// Attached behavior
class PasswordBox : DependencyObject
{
  #region Command attached property

  public static readonly DependencyProperty CommandProperty =
    DependencyProperty.RegisterAttached(
      "Command",
      typeof(ICommand),
      typeof(PasswordBox),
      new PropertyMetadata(default(ICommand), PasswordBox.OnSendPasswordCommandChanged));

  public static void SetCommand(DependencyObject attachingElement, ICommand value) =>
    attachingElement.SetValue(PasswordBox.CommandProperty, value);

  public static ICommand GetCommand(DependencyObject attachingElement) =>
    (ICommand) attachingElement.GetValue(PasswordBox.CommandProperty);

  #endregion

  private static void OnSendPasswordCommandChanged(
    DependencyObject attachingElement,
    DependencyPropertyChangedEventArgs e)
  {
    if (!(attachingElement is System.Windows.Controls.PasswordBox passwordBox))
    {
      throw new ArgumentException("Attaching element must be of type 'PasswordBox'");
    }

    if (e.OldValue != null)
    {
      return;
    }

    WeakEventManager<object, RoutedEventArgs>.AddHandler(
      passwordBox,
      nameof(System.Windows.Controls.PasswordBox.PasswordChanged),
      SendPassword_OnPasswordChanged);
  }

  private static void SendPassword_OnPasswordChanged(object sender, RoutedEventArgs e)
  {
    var attachedElement = sender as System.Windows.Controls.PasswordBox;
    SecureString commandParameter = attachedElement?.SecurePassword;
    if (commandParameter == null || commandParameter.Length < 1)
    {
      return;
    }

    ICommand sendCommand = GetCommand(attachedElement);
    sendCommand?.Execute(commandParameter);
  }
}

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);
}

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}}" />

这个实现略有不同。通过绑定ViewModel中的属性将PasswordBox传递给View。它不使用任何命令参数。ViewModel对视图保持无知。 我有一个VB VS 2010项目，可以从SkyDrive下载。WPF MVVM PassWordBox Example.zip

我在WPF MVVM应用程序中使用PasswordBox的方式非常简单，对我来说工作得很好。

基本上你创建了一个公共只读属性，视图可以绑定到PasswordBox(实际控件):

Private _thePassWordBox As PasswordBox
Public ReadOnly Property ThePassWordBox As PasswordBox
    Get
        If IsNothing(_thePassWordBox) Then _thePassWordBox = New PasswordBox
        Return _thePassWordBox
    End Get
End Property

我使用了一个支持字段来完成属性的自我初始化。

然后从Xaml中绑定ContentControl或Control Container的内容:

 <ContentControl Grid.Column="1" Grid.Row="1" Height="23" Width="120" Content="{Binding Path=ThePassWordBox}" HorizontalAlignment="Center" VerticalAlignment="Center" />

从那里你可以完全控制密码盒。我还使用PasswordAccessor(只是一个字符串的函数)返回密码值时，做登录或任何其他你想要的密码。在这个例子中，我在通用用户对象模型中有一个公共属性。 例子:

Public Property PasswordAccessor() As Func(Of String)

在用户对象中，密码字符串属性是只读的，没有任何备份存储。它只是从PasswordBox返回Password。 例子:

Public ReadOnly Property PassWord As String
    Get
        Return If((PasswordAccessor Is Nothing), String.Empty, PasswordAccessor.Invoke())
    End Get
End Property

然后在ViewModel中，我确保Accessor被创建并设置为PasswordBox。密码属性:

Public Sub New()
    'Sets the Accessor for the Password Property
    SetPasswordAccessor(Function() ThePassWordBox.Password)
End Sub

Friend Sub SetPasswordAccessor(ByVal accessor As Func(Of String))
    If Not IsNothing(VMUser) Then VMUser.PasswordAccessor = accessor
End Sub

当我需要密码字符串说登录，我只是得到用户对象密码属性，真正调用函数抓取密码并返回它，然后实际的密码不存储在用户对象。 例如:将在ViewModel中

Private Function LogIn() as Boolean
    'Make call to your Authentication methods and or functions. I usally place that code in the Model
    Return AuthenticationManager.Login(New UserIdentity(User.UserName, User.Password)
End Function

That should do it. The ViewModel doesn't need any knowledge of the View's Controls. The View just binds to the Property in the ViewModel, not any different than the View Binding to an image or other resource. In this case that resource(Property) just happens to be a usercontrol. It allows for testing as the ViewModel creates and owns the Property and the Property is independent of the View. As for security I don't know how good this implementation is. But by using a Function the value is not stored in the Property itself just accessed by the Property.