【转】WPF TextBox和PasswordBox加水印

Textbox加水印

Textbox加水印，需要一个VisualBrush和触发器验证Text是否为空，在空的时候设置背景的Brush就可以实现水印效果。

<TextBox Name="txtBoxName" Width="120" Height="23">
            <TextBox.Resources>
                <VisualBrush x:Key="HelpBrush" TileMode="None" Opacity="0.3" Stretch="None" AlignmentX="Left">
                    <VisualBrush.Visual>
                        <TextBlock FontStyle="Italic" Text="水印效果"/>
                    </VisualBrush.Visual>
                </VisualBrush>
            </TextBox.Resources>
            <TextBox.Style>
                <Style TargetType="TextBox">
                    <Setter Property="Height" Value="23"/>
                    <Setter Property="HorizontalAlignment" Value="Left"/>
                    <Setter Property="VerticalAlignment" Value="Top"/>
                    <Style.Triggers>
                        <Trigger Property="Text" Value="{x:Null}">
                            <Setter Property="Background" Value="{StaticResource HelpBrush}"/>
                        </Trigger>
                        <Trigger Property="Text" Value="">
                            <Setter Property="Background" Value="{StaticResource HelpBrush}"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </TextBox.Style>
        </TextBox>

PasswordBox加水印

PasswordBox加水印，需要添加判断输入非空的依赖属性，因为PasswordBox本身没有这个属性。

通过一个PasswordLength函数判断密码框的长度是不是0，如果是0则显示背景水印，否则就隐藏。

属性部分代码，CS文件

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());

        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);
        }
    }

XMAL代码

<PasswordBox Name="pb" Width="120" VerticalAlignment="Bottom" Height="35">
            <PasswordBox.Style>
                <Style TargetType="PasswordBox">
                    <Setter Property="Height" Value="23"/>
                    <Setter Property="HorizontalAlignment" Value="Left"/>
                    <Setter Property="VerticalAlignment" Value="Top"/>
                    <Setter Property="local: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}"/>
                                        <StackPanel Orientation="Horizontal" Visibility="Collapsed" Name="myStackPanel">
                                            <TextBlock HorizontalAlignment="Left" VerticalAlignment="Center" Foreground="LightGray" Text="水印效果"/>
                                        </StackPanel>
                                    </Grid>
                                </Border>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="IsEnabled" Value="false">
                                        <Setter Property="Visibility" TargetName="myStackPanel" Value="Collapsed"/>
                                    </Trigger>
                                    <Trigger Property="local:PasswordBoxMonitor.PasswordLength" Value="0">
                                        <Setter Property="Visibility" TargetName="myStackPanel" Value="Visible"/>
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </PasswordBox.Style>
        </PasswordBox>

效果图

2016-09-07 新增内容

将TextBlock暴露出来，做一个可以修改水印的Textbox控件

<TextBox x:Class="OracleCodeGenerator.watermarkTextBox"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:local="clr-namespace:OracleCodeGenerator"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300" Name="tb">
    <TextBox.Resources>
        <VisualBrush x:Key="HelpBrush" TileMode="None" Opacity="0.3" Stretch="None" AlignmentX="Left">
            <VisualBrush.Visual>
                <TextBlock Text="{Binding TbText,ElementName=tb}" FontStyle="Italic"/>
            </VisualBrush.Visual>
        </VisualBrush>
    </TextBox.Resources>
    <TextBox.Style>
        <Style TargetType="TextBox">
            <Setter Property="Height" Value="23"/>
            <Setter Property="HorizontalAlignment" Value="Left"/>
            <Setter Property="VerticalAlignment" Value="Top"/>
            <Style.Triggers>
                <Trigger Property="Text" Value="{x:Null}">
                    <Setter Property="Background" Value="{StaticResource HelpBrush}"/>
                </Trigger>
                <Trigger Property="Text" Value="">
                    <Setter Property="Background" Value="{StaticResource HelpBrush}"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </TextBox.Style>
</TextBox>

public partial class watermarkTextBox : TextBox
    {
        public watermarkTextBox()
        {
            InitializeComponent();
        }

        private string tbText;

        public string TbText
        {
            get
            {
                return tbText;
            }

            set
            {
                tbText = value;
            }
        }
    }

调用只有一句话

<local:watermarkTextBox Width="150" TbText="我是水印"/>