Bind TextBox.Text in Watermark attached property to localize it - wpf

Question

I need to add Watermarks to my WPF application and I am using this watermark service to achieve it.
It works just as expected, but I need to localize the text showed as watermark and I can't find a way to achieve it.
My xaml declaration:
<TextBox
Text="{Binding Name, Mode=TwoWay}">
<Watermark:WatermarkService.Watermark>
<TextBlock
Text="{Binding <What-goes-here?>}"
/>
</Watermark:WatermarkService.Watermark>
</TextBox>
My ViewModel:
public class PersonViewModel
{
public string Name {get;set;}
public string NameWatermark {get;set;}
}
Thw following lines do NOT work:
Text="{Binding NameWatermark}"
<Window x:Name="ThisWindow"
...
Text="{Binding Path=NameWatermark,
ElementName=ThisWindow}"
Is there any way to achieve it?
Any help would be appreciated, thanks.

Answer 1

I realize this question is ancient, but for google time-travelers, i hit the exact same problem and solved it by using a MultiDataTrigger to hide/show the watermark element. It works because it's not embedding the element within an adorner like the original Watermark:WatermarkService.Watermark does.
<Grid>
<TextBox x:Name="messageBox" Text="{Binding Message, UpdateSourceTrigger=PropertyChanged}" Padding="5">
<TextBox.InputBindings>
<KeyBinding Key="Enter" Command="{Binding SendMessageCommand}"/>
</TextBox.InputBindings>
</TextBox>
<TextBlock Text="{text:Translate Key=WriteMessageWatermark}" IsHitTestVisible="False" Foreground="LightGray" Margin="7,6,0,0">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Setter Property="Visibility" Value="Collapsed" />
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding ElementName=messageBox, Path=Text.IsEmpty}" Value="True" />
<Condition Binding="{Binding ElementName=messageBox, Path=IsFocused}" Value="False" />
</MultiDataTrigger.Conditions>
<Setter Property="Visibility" Value="Visible" />
</MultiDataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</Grid>

Answer 2

I think the issue is that the WatermarkService is just a static class and no dependencyobject and therefore doesn't inherit the DataContext properly to its content.
At first: Do you really need to bind to the ViewModel? I assume you want to localize more parts of your UI so moving this stuff to a dedicated service would be an option.
Something like this:
<Watermark:WatermarkService.Watermark>
<TextBlock Text="{Binding Source={x:Static Watermark:LocalizationService.Instance}, Path=[123],FallbackValue='No LocalizationService found'}"/>
</Watermark:WatermarkService.Watermark>
Singleton class for Localization:
private static volatile LocalizationService _instance;
private static object syncRoot = new Object();
public static LocalizationService Instance
{
get
{
if (_instance == null)
{
lock (syncRoot)
{
if (_instance == null)
_instance = new LocalizationService();
}
}
return _instance;
}
}
public string this[int id]
{
get
{
// do localization stuff here ...
return "Localized Value " + id;
}
}
}
If you really want to bind to the window's DataContext you can use the following workaround by assigning the ViewModel to an ObjectDataprovider and access it in your Binding:
<Grid Loaded="Grid_Loaded">
<Grid.Resources>
<ObjectDataProvider x:Key="PersonViewModelProvider" ObjectInstance="{x:Null}" IsAsynchronous="True"/>
</Grid.Resources>
<TextBox Text="{Binding Name, Mode=TwoWay}">
<Watermark:WatermarkService.Watermark>
<TextBlock Text="{Binding Source={StaticResource PersonViewModelProvider}, Path=NameWatermark}"/>
</Watermark:WatermarkService.Watermark>
</TextBox>
</Grid>
Code Behind:
private void Grid_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
var panel = sender as Panel;
if (panel != null)
{
var objDataProvider = panel.Resources["PersonViewModelProvider"] as ObjectDataProvider;
objDataProvider.ObjectInstance = panel.DataContext;
}
}