Password Box unmasked content

<Style x:Key="WaterMarkTextBoxStyle"

       BasedOn="{StaticResource {x:Type TextBox}}"

       TargetType="{x:Type TextBox}">

    <Setter Property="Template">

        <Setter.Value>

            <ControlTemplate TargetType="{x:Type TextBox}">

                <Grid>

                    <ScrollViewer x:Name="PART_ContentHost"

                                  SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />

                    <TextBlock x:Name="textBlock"

                               Opacity="0.345"

                               Text="Password"

                               TextWrapping="Wrap"

                               Visibility="Hidden" />

                Grid>

                <ControlTemplate.Triggers>

                    <MultiTrigger>

                        <MultiTrigger.Conditions>

                            <Condition Property="IsFocused"

                                       Value="False" />

                            <Condition Property="Text"

                                       Value="" />

                        MultiTrigger.Conditions>

                        <Setter Property="Visibility"

                                TargetName="textBlock"

                                Value="Visible" />

                    MultiTrigger>

                ControlTemplate.Triggers>

            ControlTemplate>

        Setter.Value>

    Setter>

Style>


Refer this too http://joyfulwpf.blogspot.com/2009/02/wpf-watermark-textbox-using-xaml-style.html