(using Visual Studio 2010 and .NET/Silverlight 4)
Maybe there is a working solution for this already out there, but I created my own Silverlight Behavior for a basic TextBox Watermark which might be useful.
I wanted to use it like this in my XAML (look at the behaviors tag):
<TextBlock Margin="5">Watermarked textbox:</TextBlock>
<TextBox Margin="5">
<Interactivity:Interaction.Behaviors>
<local:Watermark Text="Watermark" Foreground="LightGray" />
</Interactivity:Interaction.Behaviors>
</TextBox>
The result should be something like this:
To create a Behavior for Silverlight, you must get hold of the System.Windows.Interactivity assembly which ships with Expression Blend. In my system it’s located at:
c:\Program Files (x86)\Microsoft SDKs\Expression\Blend\Silverlight\v4.0\Libraries\System.Windows.Interactivity.dll
And the code for the Behavior:
public class Watermark : Behavior<TextBox>
{
private bool _hasWatermark;
private Brush _textBoxForeground;
public String Text { get; set; }
public Brush Foreground { get; set; }
protected override void OnAttached()
{
_textBoxForeground = AssociatedObject.Foreground;
base.OnAttached();
if (Text != null)
SetWatermarkText();
AssociatedObject.GotFocus += GotFocus;
AssociatedObject.LostFocus += LostFocus;
}
private void LostFocus(object sender, RoutedEventArgs e)
{
if (AssociatedObject.Text.Length == 0)
if (Text != null)
SetWatermarkText();
}
private void GotFocus(object sender, RoutedEventArgs e)
{
if (_hasWatermark)
RemoveWatermarkText();
}
private void RemoveWatermarkText()
{
AssociatedObject.Foreground = _textBoxForeground;
AssociatedObject.Text = "";
_hasWatermark = false;
}
private void SetWatermarkText()
{
AssociatedObject.Foreground = Foreground;
AssociatedObject.Text = Text;
_hasWatermark = true;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.GotFocus -= GotFocus;
AssociatedObject.LostFocus -= LostFocus;
}
}
Like so many Watermark-solutions out there I’m hooking into the GotFocus/LostFocus events and to the work there. Works for me. Love Behaviors.