来自 Watermark TextBox 的 WPF Watermark PasswordBox [英] WPF Watermark PasswordBox from Watermark TextBox

问题描述

我正在使用 WPF 中的水印文本框

 <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>

如何将其应用于 PasswordBox?

How can I apply this for a PasswordBox?

推荐答案

一般方法是一样的:你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.以下代码演示了如何操作.

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.

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#

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);
    }
  }
}

请注意 XAML 代码中的 PasswordBoxMonitor.

Please notice PasswordBoxMonitor in XAML code.

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