wpf带水印的密码框样式

你可以通过自定义WPF样式来创建带水印的密码框。下面是一个示例样式，其中包含了带有水印的文本框和密码框：

<Style x:Key="WatermarkPasswordBox" TargetType="{x:Type PasswordBox}">
    <Setter Property="Background" Value="White"/>
    <Setter Property="BorderThickness" Value="1"/>
    <Setter Property="BorderBrush" Value="#FF7F9DB9"/>
    <Setter Property="Foreground" Value="Black"/>
    <Setter Property="Padding" Value="2"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type PasswordBox}">
                <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*"/>
                            <ColumnDefinition Width="Auto"/>
                        </Grid.ColumnDefinitions>
                        <TextBox x:Name="PART_TextBox" Grid.Column="0" Foreground="{TemplateBinding Foreground}" Text="{TemplateBinding Password}" Margin="{TemplateBinding Padding}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{TemplateBinding IsReadOnly}" IsEnabled="{TemplateBinding IsEnabled}" Background="Transparent"/>
                        <TextBlock x:Name="PART_Watermark" Grid.Column="0" Foreground="Gray" Text="Password" Margin="{TemplateBinding Padding}" VerticalAlignment="Center" Visibility="Collapsed"/>
                        <ToggleButton x:Name="PART_ShowPasswordButton" Grid.Column="1" Width="20" Height="20" Style="{StaticResource ToggleButtonStyle}" IsChecked="{Binding IsChecked, ElementName=PART_ShowPasswordButton}" VerticalAlignment="Center" HorizontalAlignment="Right"/>
                    </Grid>
                </Border>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsFocused" Value="True">
                        <Setter Property="Visibility" TargetName="PART_Watermark" Value="Collapsed"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                        <Setter Property="Background" Value="#FFF4F4F4"/>
                    </Trigger>
                    <DataTrigger Binding="{Binding IsChecked, ElementName=PART_ShowPasswordButton}" Value="True">
                        <Setter TargetName="PART_TextBox" Property="Visibility" Value="Collapsed"/>
                        <Setter TargetName="PART_Watermark" Property="Visibility" Value="Visible"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding IsChecked, ElementName=PART_ShowPasswordButton}" Value="False">
                        <Setter TargetName="PART_TextBox" Property="Visibility" Value="Visible"/>
                        <Setter TargetName="PART_Watermark" Property="Visibility" Value="Collapsed"/>
                    </DataTrigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

在这个样式中，使用了一个文本框控件和一个密码框控件来创建带有水印的密码框。水印文本是在TextBox控件上覆盖了一个TextBlock控件实现的，当用户输入密码时，水印文本会被隐藏。此外，还添加了一个ToggleButton控件，用于显示或隐藏密码。

使用这个样式时，只需要将PasswordBox控件的样式设置为WatermarkPasswordBox即可。例如：

<PasswordBox Style="{StaticResource WatermarkPasswordBox}"/>

这样就可以创建一个带有水印的密码框了。