我使用了一个身份验证检查，然后是一个中介类向View调用的子(它也实现了身份验证检查)，将密码写入数据类。

这不是一个完美的解决方案;但是，它弥补了我无法移动密码的问题。

正如你所看到的，我绑定到密码，但也许它绑定到静态类..

它是一个附加属性。这种属性可以应用于任何类型的DependencyObject，而不仅仅是声明它的类型。因此，尽管它是在PasswordHelper静态类中声明的，但它还是应用于使用它的PasswordBox。

要使用这个附加属性，你只需要将它绑定到ViewModel中的Password属性:

<PasswordBox w:PasswordHelper.Attach="True" 
         w:PasswordHelper.Password="{Binding Password}"/>

一个不违反MVVM模式的简单解决方案是在ViewModel中引入一个获取密码的事件(或委托)。

在ViewModel中:

public event eventandler <HarvestPasswordEventArgs> HarvestPassword;

使用这些EventArgs:

class HarvestPasswordEventArgs : EventArgs
{
    public string Password;
}

在View中，订阅创建ViewModel时的事件，并填写密码值。

_viewModel.HarvestPassword += (sender, args) => 
    args.Password = passwordBox1.Password;

在ViewModel中，当你需要密码时，你可以触发事件并从那里获取密码:

if (HarvestPassword == null)
  //bah 
  return;

var pwargs = new HarvestPasswordEventArgs();
HarvestPassword(this, pwargs);

LoginHelpers.Login(Username, pwargs.Password);

我花了大量时间研究各种解决方案。我不喜欢装饰器的想法，行为弄乱了验证UI，背后的代码……真的吗?

最好的方法是坚持自定义附加属性，并绑定到视图模型中的SecureString属性。尽量把它放在里面。当你需要快速访问纯密码时，使用下面的代码将其临时转换为不安全的字符串:

namespace Namespace.Extensions
{
    using System;
    using System.Runtime.InteropServices;
    using System.Security;

    /// <summary>
    /// Provides unsafe temporary operations on secured strings.
    /// </summary>
    [SuppressUnmanagedCodeSecurity]
    public static class SecureStringExtensions
    {
        /// <summary>
        /// Converts a secured string to an unsecured string.
        /// </summary>
        public static string ToUnsecuredString(this SecureString secureString)
        {
            // copy&paste from the internal System.Net.UnsafeNclNativeMethods
            IntPtr bstrPtr = IntPtr.Zero;
            if (secureString != null)
            {
                if (secureString.Length != 0)
                {
                    try
                    {
                        bstrPtr = Marshal.SecureStringToBSTR(secureString);
                        return Marshal.PtrToStringBSTR(bstrPtr);
                    }
                    finally
                    {
                        if (bstrPtr != IntPtr.Zero)
                            Marshal.ZeroFreeBSTR(bstrPtr);
                    }
                }
            }
            return string.Empty;
        }

        /// <summary>
        /// Copies the existing instance of a secure string into the destination, clearing the destination beforehand.
        /// </summary>
        public static void CopyInto(this SecureString source, SecureString destination)
        {
            destination.Clear();
            foreach (var chr in source.ToUnsecuredString())
            {
                destination.AppendChar(chr);
            }
        }

        /// <summary>
        /// Converts an unsecured string to a secured string.
        /// </summary>
        public static SecureString ToSecuredString(this string plainString)
        {
            if (string.IsNullOrEmpty(plainString))
            {
                return new SecureString();
            }

            SecureString secure = new SecureString();
            foreach (char c in plainString)
            {
                secure.AppendChar(c);
            }
            return secure;
        }
    }
}

确保允许GC收集UI元素，因此不要为PasswordBox上的PasswordChanged事件使用静态事件处理程序。 我还发现了一个异常，当使用SecurePassword属性设置它时，控件没有更新UI，这就是为什么我将密码复制到password的原因。

namespace Namespace.Controls
{
    using System.Security;
    using System.Windows;
    using System.Windows.Controls;
    using Namespace.Extensions;

    /// <summary>
    /// Creates a bindable attached property for the <see cref="PasswordBox.SecurePassword"/> property.
    /// </summary>
    public static class PasswordBoxHelper
    {
        // an attached behavior won't work due to view model validation not picking up the right control to adorn
        public static readonly DependencyProperty SecurePasswordBindingProperty = DependencyProperty.RegisterAttached(
            "SecurePassword",
            typeof(SecureString),
            typeof(PasswordBoxHelper),
            new FrameworkPropertyMetadata(new SecureString(),FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, AttachedPropertyValueChanged)
        );

        private static readonly DependencyProperty _passwordBindingMarshallerProperty = DependencyProperty.RegisterAttached(
            "PasswordBindingMarshaller",
            typeof(PasswordBindingMarshaller),
            typeof(PasswordBoxHelper),
            new PropertyMetadata()
        );

        public static void SetSecurePassword(PasswordBox element, SecureString secureString)
        {
            element.SetValue(SecurePasswordBindingProperty, secureString);
        }

        public static SecureString GetSecurePassword(PasswordBox element)
        {
            return element.GetValue(SecurePasswordBindingProperty) as SecureString;
        }

        private static void AttachedPropertyValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            // we'll need to hook up to one of the element's events
            // in order to allow the GC to collect the control, we'll wrap the event handler inside an object living in an attached property
            // don't be tempted to use the Unloaded event as that will be fired  even when the control is still alive and well (e.g. switching tabs in a tab control) 
            var passwordBox = (PasswordBox)d;
            var bindingMarshaller = passwordBox.GetValue(_passwordBindingMarshallerProperty) as PasswordBindingMarshaller;
            if (bindingMarshaller == null)
            {
                bindingMarshaller = new PasswordBindingMarshaller(passwordBox);
                passwordBox.SetValue(_passwordBindingMarshallerProperty, bindingMarshaller);
            }

            bindingMarshaller.UpdatePasswordBox(e.NewValue as SecureString);
        }

        /// <summary>
        /// Encapsulated event logic
        /// </summary>
        private class PasswordBindingMarshaller
        {
            private readonly PasswordBox _passwordBox;
            private bool _isMarshalling;

            public PasswordBindingMarshaller(PasswordBox passwordBox)
            {
                _passwordBox = passwordBox;
                _passwordBox.PasswordChanged += this.PasswordBoxPasswordChanged;
            }

            public void UpdatePasswordBox(SecureString newPassword)
            {
                if (_isMarshalling)
                {
                    return;
                }

                _isMarshalling = true;
                try
                {
                    // setting up the SecuredPassword won't trigger a visual update so we'll have to use the Password property
                    _passwordBox.Password = newPassword.ToUnsecuredString();

                    // you may try the statement below, however the benefits are minimal security wise (you still have to extract the unsecured password for copying)
                    //newPassword.CopyInto(_passwordBox.SecurePassword);
                }
                finally
                {
                    _isMarshalling = false;
                }
            }

            private void PasswordBoxPasswordChanged(object sender, RoutedEventArgs e)
            {
                // copy the password into the attached property
                if (_isMarshalling)
                {
                    return;
                }

                _isMarshalling = true;
                try
                {
                    SetSecurePassword(_passwordBox, _passwordBox.SecurePassword.Copy());
                }
                finally
                {
                    _isMarshalling = false;
                }
            }
        }
    }
}

以及XAML用法:

<PasswordBox controls:PasswordBoxHelper.SecurePassword="{Binding LogonPassword, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}">

我在视图模型中的属性是这样的:

[RequiredSecureString]
public SecureString LogonPassword
{
   get
   {
       return _logonPassword;
   }
   set
   {
       _logonPassword = value;
       NotifyPropertyChanged(nameof(LogonPassword));
   }
}

RequiredSecureString只是一个简单的自定义验证器，它有以下逻辑:

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = true)]    
public class RequiredSecureStringAttribute:ValidationAttribute
{
    public RequiredSecureStringAttribute()
        :base("Field is required")
    {            
    }

    public override bool IsValid(object value)
    {
        return (value as SecureString)?.Length > 0;
    }
}

给你。一个完整的和经过测试的纯MVVM解决方案。

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);
    }
}

我花了很长时间才把它弄好。最后，我放弃了，只使用了DevExpress的PasswordBoxEdit。

这是迄今为止最简单的解决方案，因为它允许绑定而不使用任何可怕的技巧。

DevExpress网站上的解决方案

郑重声明，我和开发快递没有任何关系。