Watermarked TextBox with an AttachedProperty
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Ever wanted to create a watermark effect for a TextBox in WPF? Most of the tutorials scattered around have either used static text or created a subclass of TextBox. I wanted to use an AttachedProperty instead, and though it took a while to try every possible combination of brackets and bindings I came up with the following to create an AttachedProperty which you can apply in any ResourceDictionary or wherever you keep your Styles.
public class WatermarkedTextBox { public static readonly DependencyProperty WatermarkProperty = DependencyProperty.RegisterAttached("Watermark", typeof(string), typeof(WatermarkedTextBox)); public static void SetWatermark(TextBox element, string watermark) { element.SetValue(WatermarkProperty, watermark); } public static string GetWatermark(UIElement element) { return element.GetValue(WatermarkProperty) as string; } }
You need to include the namespace for whichever assemly contains the AttachedProperty (l49ui in my case).
<Style TargetType="{x:Type TextBoxBase}" x:Key="{x:Type TextBox}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type TextBoxBase}"> <Grid> <ScrollViewer Margin="0" x:Name="PART_ContentHost" Background="Transparent"/> <TextBlock x:Name="watermark" Opacity="0.3" Text="{Binding (l49ui:WatermarkedTextBox.Watermark),RelativeSource={RelativeSource TemplatedParent}}" TextWrapping="Wrap" Visibility="Collapsed" /> </Grid> <ControlTemplate.Triggers> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsFocused" Value="False" /> <Condition Property="TextBox.Text" Value="" /> </MultiTrigger.Conditions> <Setter Property="Visibility" TargetName="watermark" Value="Visible" /> </MultiTrigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style>
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