我遇到了绑定到密码盒的问题。这似乎是一个安全风险，但我正在使用MVVM模式，所以我希望绕过这个。我在这里发现了一些有趣的代码(有人使用过这个或类似的代码吗?)
http://www.wpftutorial.net/PasswordBox.html
从技术上讲，它看起来很棒，但我不确定如何检索密码。
我基本上有属性在我的LoginViewModel用户名和密码。用户名是好的，正在工作，因为它是一个文本框。
我使用上面的代码，并输入这个
<PasswordBox ff:PasswordHelper.Attach="True"
ff:PasswordHelper.Password="{Binding Path=Password}" Width="130"/>
当我有PasswordBox作为一个文本框和绑定路径=密码，然后在我的LoginViewModel属性更新。
我的代码非常简单，基本上我有一个命令为我的按钮。当我按下它CanLogin被调用，如果它返回真，它调用Login。
你可以看到，我检查了我的用户名属性，这很好。
在登录我发送到我的服务的用户名和密码，用户名包含数据从我的视图，但密码是空|空
private DelegateCommand loginCommand;
public string Username { get; set; }
public string Password { get; set; }
public ICommand LoginCommand
{
get
{
if (loginCommand == null)
{
loginCommand = new DelegateCommand(
Login, CanLogin );
}
return loginCommand;
}
}
private bool CanLogin()
{
return !string.IsNullOrEmpty(Username);
}
private void Login()
{
bool result = securityService.IsValidLogin(Username, Password);
if (result) { }
else { }
}
这就是我正在做的
<TextBox Text="{Binding Path=Username, UpdateSourceTrigger=PropertyChanged}"
MinWidth="180" />
<PasswordBox ff:PasswordHelper.Attach="True"
ff:PasswordHelper.Password="{Binding Path=Password}" Width="130"/>
我有我的文本框，这是没有问题的，但在我的ViewModel密码是空的。
是我做错了什么还是漏了一步?
我放了一个断点，果然代码进入静态助手类，但它从不更新我的ViewModel中的密码。
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);
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;
}
}
}
}
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。
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。
