Hi people stackoverflow. I'm working with MVVM, I have ViewModel call UserViewModel with a Property Password. In the View have a control PasswordBox.
<PasswordBox x:Name="txtPassword" Password="{Binding Password}" />
But this xaml don't work. How do you do the binding?? Help please!!
出于安全原因，Password 属性不是依赖属性，因此您不能绑定到它。不幸的是，您需要在老式方式后面的代码中执行绑定（注册 OnPropertyChanged 事件并通过代码更新值......）
我快速搜索将我带到这篇博客文章，该文章展示了如何编写附加属性来回避这个问题。这是否值得做虽然真的取决于你对代码隐藏的厌恶。
您始终可以编写一个包含 Password 并为 Password 属性添加依赖项属性的控件。
我只会使用后面的代码，但如果你必须这样做，你可以这样做：
public class BindablePasswordBox : Decorator
{
public static readonly DependencyProperty PasswordProperty =
DependencyProperty.Register("Password", typeof(string), typeof(BindablePasswordBox));
public string Password
{
get { return (string)GetValue(PasswordProperty); }
set { SetValue(PasswordProperty, value); }
}
public BindablePasswordBox()
{
Child = new PasswordBox();
((PasswordBox)Child).PasswordChanged += BindablePasswordBox_PasswordChanged;
}
void BindablePasswordBox_PasswordChanged(object sender, RoutedEventArgs e)
{
Password = ((PasswordBox)Child).Password;
}
}
BindablePasswordBox 存在问题。它只在一个方向上起作用，从 PasswordBox 到 PasswordProperty。下面是它的修改版本，可以双向工作。它注册一个 PropertyChangedCallback 并在调用时更新 PasswordBox 的密码。我希望有人觉得这很有用。
public class BindablePasswordBox : Decorator
{
public static readonly DependencyProperty PasswordProperty = DependencyProperty.Register("Password", typeof(string), typeof(BindablePasswordBox), new PropertyMetadata(string.Empty, OnDependencyPropertyChanged));
public string Password
{
get { return (string)GetValue(PasswordProperty); }
set { SetValue(PasswordProperty, value); }
}
private static void OnDependencyPropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs e)
{
BindablePasswordBox p = source as BindablePasswordBox;
if (p != null)
{
if (e.Property == PasswordProperty)
{
var pb = p.Child as PasswordBox;
if (pb != null)
{
if (pb.Password != p.Password)
pb.Password = p.Password;
}
}
}
}
public BindablePasswordBox()
{
Child = new PasswordBox();
((PasswordBox)Child).PasswordChanged += BindablePasswordBox_PasswordChanged;
}
void BindablePasswordBox_PasswordChanged(object sender, RoutedEventArgs e)
{
Password = ((PasswordBox)Child).Password;
}
}
为了避免密码在内存中作为纯文本在任何时候都可用，我将值作为参数提供给我的命令。
<Label>User Name</Label>
<TextBox Text="{Binding UserName}" />
<Label>Password</Label>
<PasswordBox Name="PasswordBox" />
<StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Margin="0 16 0 0">
<Button Margin="0 0 8 0" MinWidth="65"
Command="{Binding LoginAccept}"
CommandParameter="{Binding ElementName=PasswordBox}">
Login
</Button>
<Button MinWidth="65" Command="{Binding LoginCancel}">Cancel</Button>
</StackPanel>
然后在我的视图模型中。
public DelegateCommand<object> LoginAccept { get; private set; }
public DelegateCommand<object> LoginCancel { get; private set; }
public LoginViewModel {
LoginAccept = new DelegateCommand<object>(o => OnLogin(o), (o) => IsLoginVisible);
LoginCancel = new DelegateCommand<object>(o => OnLoginCancel(), (o) => IsLoginVisible);
}
private void OnLogin(object o)
{
var passwordBox = (o as System.Windows.Controls.PasswordBox);
var password = passwordBox.SecurePassword.Copy();
passwordBox.Clear();
ShowLogin = false;
var credential = new System.Net.NetworkCredential(UserName, password);
}
private void OnLoginCancel()
{
ShowLogin = false;
}
虽然直接从绑定中提供 SecurePassword 是有意义的，但它似乎总是提供一个空值。所以这不起作用：
<Button Margin="0 0 8 0" MinWidth="65"
Command="{Binding LoginAccept}"
CommandParameter="{Binding ElementName=PasswordBox, Path=SecurePassword}">
检查密码框上的另一个线程。最好不要将密码保存在任何 DP 或公共财产上。