how to add a customtext to datepicker text box

Question

i designed a textbox foe date picker but i cant add a custom text inside the textbox before choosing date.i want to add "select a date"

<Grid>
        <DatePicker x:Name="DateGviya" SelectedDate="{Binding CurrentDate}"  HorizontalAlignment="Left" VerticalAlignment="Top" Margin="97,77,0,0">
            <DatePicker.Resources>
                <Style TargetType="{x:Type DatePickerTextBox}">
                    <Setter Property="Control.Template">
                        <Setter.Value>
                            <ControlTemplate>
                                <TextBox x:Name="PART_TextBox" Text="{Binding Path=SelectedDate, StringFormat='dd/MM/yyyy hh:mm:ss tt', RelativeSource={RelativeSource AncestorType={x:Type DatePicker}}}" />
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </DatePicker.Resources>
        </DatePicker>
    </Grid>

result is like this:

Answer 1

You could use the TargetNullValue property of the binding:

<DatePicker x:Name="DateGviya" SelectedDate="{Binding CurrentDate}"  HorizontalAlignment="Left" VerticalAlignment="Top" Margin="97,77,0,0">
    <DatePicker.Resources>
        <Style TargetType="{x:Type DatePickerTextBox}">
            <Setter Property="Control.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <TextBox x:Name="PART_TextBox" 
                                 Text="{Binding Path=SelectedDate, 
                                    StringFormat='dd/MM/yyyy hh:mm:ss tt', 
                                    RelativeSource={RelativeSource AncestorType={x:Type DatePicker}},
                                    TargetNullValue='Select a Date'}" />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </DatePicker.Resources>
</DatePicker>