来自 Watermark TextBox 的 WPF Watermark PasswordBox

WPF Watermark PasswordBox from Watermark TextBox

提问by Sauron

I am using a Watermark textbox as in Watermark TextBox in WPF

我正在使用WPF中的Watermark TextBox 中的 Watermark 文本框

 <Grid Grid.Row="0" Background="{StaticResource brushWatermarkBackground}" Style="{StaticResource EntryFieldStyle}" >
        <TextBlock Margin="5,2" Text="This prompt dissappears as you type..." Foreground="{StaticResource brushWatermarkForeground}"
                   Visibility="{Binding ElementName=txtUserEntry, Path=Text.IsEmpty, Converter={StaticResource BooleanToVisibilityConverter}}" />
        <TextBox Name="txtUserEntry" Background="Transparent" BorderBrush="{StaticResource brushWatermarkBorder}" />
    </Grid>

How can I apply this for a PasswordBox?

如何将其应用于 PasswordBox？

回答by Anvaka

General approach is the same: you write custom control style, and show watermark whenever password box is empty. The only problem here is that PasswordBox.Password property is not a dependency property, and you can't use it in trigger. Also PasswordBox is sealed, so you can't override this notification behaviour. But you can use attached properties here. The following code demonstrates how.

一般方法是相同的：您编写自定义控件样式，并在密码框为空时显示水印。这里唯一的问题是 PasswordBox.Password 属性不是依赖属性，您不能在触发器中使用它。PasswordBox 也是密封的，因此您无法覆盖此通知行为。但是您可以在此处使用附加属性。下面的代码演示了如何。

XAML

XAML

<Window x:Class="WpfTest.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:WpfTest="clr-namespace:WpfTest"
    Title="Password Box Sample" Height="300" Width="300">
  <Window.Resources>
    <Style x:Key="{x:Type PasswordBox}"
        TargetType="{x:Type PasswordBox}">
      <Setter Property="WpfTest:PasswordBoxMonitor.IsMonitoring"
              Value="True"/>
      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate TargetType="{x:Type PasswordBox}">
            <Border Name="Bd"
                    Background="{TemplateBinding Background}"
                    BorderThickness="{TemplateBinding BorderThickness}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    SnapsToDevicePixels="true">
              <Grid>
                <ScrollViewer x:Name="PART_ContentHost"
                              SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                <TextBlock Text="Please enter your password" 
                           Margin="4, 2, 0, 0"
                           Foreground="Gray" 
                           Visibility="Collapsed"
                           Name="txtPrompt" />
              </Grid>
            </Border>
            <ControlTemplate.Triggers>
              <Trigger Property="IsEnabled"
                                         Value="false">
                <Setter TargetName="Bd"
                                            Property="Background"
                                            Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
                <Setter Property="Foreground"
                                            Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
              </Trigger>
              <Trigger Property="WpfTest:PasswordBoxMonitor.PasswordLength" Value="0">
                <Setter Property="Visibility" TargetName="txtPrompt" Value="Visible"/>
              </Trigger>
            </ControlTemplate.Triggers>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>
  </Window.Resources>
  <Grid>
    <PasswordBox VerticalAlignment="Top"/>
  </Grid>
</Window>

C#

C＃

using System.Windows;
using System.Windows.Controls;

namespace WpfTest
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }

    }

  public class PasswordBoxMonitor : DependencyObject
  {
    public static bool GetIsMonitoring(DependencyObject obj)
    {
      return (bool)obj.GetValue(IsMonitoringProperty);
    }

    public static void SetIsMonitoring(DependencyObject obj, bool value)
    {
      obj.SetValue(IsMonitoringProperty, value);
    }

    public static readonly DependencyProperty IsMonitoringProperty =
        DependencyProperty.RegisterAttached("IsMonitoring", typeof(bool), typeof(PasswordBoxMonitor), new UIPropertyMetadata(false, OnIsMonitoringChanged));



    public static int GetPasswordLength(DependencyObject obj)
    {
      return (int)obj.GetValue(PasswordLengthProperty);
    }

    public static void SetPasswordLength(DependencyObject obj, int value)
    {
      obj.SetValue(PasswordLengthProperty, value);
    }

    public static readonly DependencyProperty PasswordLengthProperty =
        DependencyProperty.RegisterAttached("PasswordLength", typeof(int), typeof(PasswordBoxMonitor), new UIPropertyMetadata(0));

    private static void OnIsMonitoringChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      var pb = d as PasswordBox;
      if (pb == null)
      {
        return;
      }
      if ((bool) e.NewValue)
      {
        pb.PasswordChanged += PasswordChanged;
      }
      else
      {
        pb.PasswordChanged -= PasswordChanged;
      }
    }

    static void PasswordChanged(object sender, RoutedEventArgs e)
    {
      var pb = sender as PasswordBox;
      if (pb == null)
      {
        return;
      }
      SetPasswordLength(pb, pb.Password.Length);
    }
  }
}

Please notice PasswordBoxMonitor in XAML code.

请注意 XAML 代码中的 PasswordBoxMonitor。

回答by Werner Wichtig

you can show/hide the background by yourself instead of using triggers:

您可以自己显示/隐藏背景，而不是使用触发器：

XAML:

XAML：

<PasswordBox x:Name="passwordBox" PasswordChanged="passwordChanged" 
        Background="{StaticResource PasswordHint}" />

Code behind:

后面的代码：

// helper to hide watermark hint in password field
private void passwordChanged(object sender, RoutedEventArgs e)
{           
    if (passwordBox.Password.Length == 0)
        passwordBox.Background.Opacity = 1;
    else
        passwordBox.Background.Opacity = 0;
}

回答by blindmeis

you can use my approach for a watermark behavior. all you have to do is copy and paste the TextBoxWatermarkBehaviorand the change the Behavior<TextBox>to Behavior<PasswordBox>.

您可以将我的方法用于水印行为。您所要做的就是复制并粘贴TextBoxWatermarkBehavior并将 更改Behavior<TextBox>为Behavior<PasswordBox>。

you can find a demo project here

你可以在这里找到一个演示项目

回答by VivekDev

@blindmeis's suggestion is good. For PasswordBox the class would be as follows.

@blindmeis 的建议很好。对于 PasswordBox，类将如下所示。

public class PasswordBoxWatermarkBehavior : System.Windows.Interactivity.Behavior<PasswordBox>
{
    private TextBlockAdorner adorner;
    private WeakPropertyChangeNotifier notifier;

    #region DependencyProperty's

    public static readonly DependencyProperty LabelProperty =
        DependencyProperty.RegisterAttached("Label", typeof(string), typeof(PasswordBoxWatermarkBehavior));

    public string Label
    {
        get { return (string)GetValue(LabelProperty); }
        set { SetValue(LabelProperty, value); }
    }

    public static readonly DependencyProperty LabelStyleProperty =
        DependencyProperty.RegisterAttached("LabelStyle", typeof(Style), typeof(PasswordBoxWatermarkBehavior));

    public Style LabelStyle
    {
        get { return (Style)GetValue(LabelStyleProperty); }
        set { SetValue(LabelStyleProperty, value); }
    }

    #endregion

    protected override void OnAttached()
    {
        base.OnAttached();
        this.AssociatedObject.Loaded += this.AssociatedObjectLoaded;
        this.AssociatedObject.PasswordChanged += AssociatedObjectPasswordChanged;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        this.AssociatedObject.Loaded -= this.AssociatedObjectLoaded;
        this.AssociatedObject.PasswordChanged -= this.AssociatedObjectPasswordChanged;

        this.notifier = null;
    }

    private void AssociatedObjectPasswordChanged(object sender, RoutedEventArgs e)
    {
        this.UpdateAdorner();
    }

    private void AssociatedObjectLoaded(object sender, System.Windows.RoutedEventArgs e)
    {
        this.adorner = new TextBlockAdorner(this.AssociatedObject, this.Label, this.LabelStyle);

        this.UpdateAdorner();

        //AddValueChanged for IsFocused in a weak manner
        this.notifier = new WeakPropertyChangeNotifier(this.AssociatedObject, UIElement.IsFocusedProperty);
        this.notifier.ValueChanged += new EventHandler(this.UpdateAdorner);
    }

    private void UpdateAdorner(object sender, EventArgs e)
    {
        this.UpdateAdorner();
    }


    private void UpdateAdorner()
    {
        if (!String.IsNullOrEmpty(this.AssociatedObject.Password) || this.AssociatedObject.IsFocused)
        {
            // Hide the Watermark Label if the adorner layer is visible
            this.AssociatedObject.TryRemoveAdorners<TextBlockAdorner>();
        }
        else
        {
            // Show the Watermark Label if the adorner layer is visible
            this.AssociatedObject.TryAddAdorner<TextBlockAdorner>(adorner);
        }
    }
}