Question

嗨人stackoverflow。我正在使用MVVM，我有 ViewModel 使用属性密码调用UserViewModel。在视图中有一个控件PasswordBox。

<PasswordBox x:Name="txtPassword" Password="{Binding Password}" />

但是这个xaml不起作用。你怎么做绑定？请帮忙！！

Answer 1

出于安全原因，Password属性不是依赖项属性，因此您无法绑定它。不幸的是，你需要在老式方式背后的代码中执行绑定（注册OnPropertyChanged事件并通过代码更新值...）

我快速搜索将我带到this blog post，其中显示了如何编写附加属性来回避问题。这是否值得做，但实际上取决于你对代码隐藏的厌恶。

Answer 2

您始终可以编写一个包装密码的控件，并为Password属性添加依赖项属性。

我只会使用代码，但如果你必须，你可以做类似的事情：

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;
    }

}

Answer 3

BindablePasswordBox存在问题。它只能在一个方向上工作，PasswordBox到PasswordProperty。以下是它的两个方向的修改版本。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;
    }
}

Answer 4

为避免在内存中将密码作为纯文本提供，我将该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}">

Answer 5

检查密码框中的另一个帖子。最好不要将密码保存在任何DP或公共财产上。

Other thread on passwordbox

带有MVVM的PasswordBox

5 个答案: