Postanowiłem rozwiązać ten problem poprzez zachowanie. Wykorzystuje Hintwłaściwość do zdefiniowania tekstu do wyświetlenia (może być również obiektem, jeśli wolisz) oraz Valuewłaściwość do oceny, czy podpowiedź powinna być widoczna, czy nie.
Zachowanie deklaruje się w następujący sposób:
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Interactivity;
using System.Windows.Media;
public class HintBehavior : Behavior<ContentControl>
{
public static readonly DependencyProperty HintProperty = DependencyProperty
.Register("Hint", typeof (string), typeof (HintBehavior)
//, new FrameworkPropertyMetadata(null, OnHintChanged)
);
public string Hint
{
get { return (string) GetValue(HintProperty); }
set { SetValue(HintProperty, value); }
}
public static readonly DependencyProperty ValueProperty = DependencyProperty
.Register("Value", typeof (object), typeof (HintBehavior)
, new FrameworkPropertyMetadata(null, OnValueChanged));
private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var visible = e.NewValue == null;
d.SetValue(VisibilityProperty, visible ? Visibility.Visible : Visibility.Collapsed);
}
public object Value
{
get { return GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public static readonly DependencyProperty VisibilityProperty = DependencyProperty
.Register("Visibility", typeof (Visibility), typeof (HintBehavior)
, new FrameworkPropertyMetadata(Visibility.Visible
//, new PropertyChangedCallback(OnVisibilityChanged)
));
public Visibility Visibility
{
get { return (Visibility) GetValue(VisibilityProperty); }
set { SetValue(VisibilityProperty, value); }
}
public static readonly DependencyProperty ForegroundProperty = DependencyProperty
.Register("Foreground", typeof (Brush), typeof (HintBehavior)
, new FrameworkPropertyMetadata(new SolidColorBrush(Colors.DarkGray)
//, new PropertyChangedCallback(OnForegroundChanged)
));
public Brush Foreground
{
get { return (Brush) GetValue(ForegroundProperty); }
set { SetValue(ForegroundProperty, value); }
}
public static readonly DependencyProperty MarginProperty = DependencyProperty
.Register("Margin", typeof (Thickness), typeof (HintBehavior)
, new FrameworkPropertyMetadata(new Thickness(4, 5, 0, 0)
//, new PropertyChangedCallback(OnMarginChanged)
));
public Thickness Margin
{
get { return (Thickness) GetValue(MarginProperty); }
set { SetValue(MarginProperty, value); }
}
private static ResourceDictionary _hintBehaviorResources;
public static ResourceDictionary HintBehaviorResources
{
get
{
if (_hintBehaviorResources == null)
{
var res = new ResourceDictionary
{
Source = new Uri("/Mayflower.Client.Core;component/Behaviors/HintBehaviorResources.xaml",
UriKind.RelativeOrAbsolute)
};
_hintBehaviorResources = res;
}
return _hintBehaviorResources;
}
}
protected override void OnAttached()
{
base.OnAttached();
var t = (ControlTemplate) HintBehaviorResources["HintBehaviorWrapper"];
AssociatedObject.Template = t;
AssociatedObject.Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
AssociatedObject.Loaded -= OnLoaded;
var label = (Label) AssociatedObject.Template.FindName("PART_HintLabel", AssociatedObject);
label.DataContext = this;
//label.Content = "Hello...";
label.SetBinding(UIElement.VisibilityProperty, new Binding("Visibility") {Source = this, Mode = BindingMode.OneWay});
label.SetBinding(ContentControl.ContentProperty, new Binding("Hint") {Source = this, Mode = BindingMode.OneWay});
label.SetBinding(Control.ForegroundProperty, new Binding("Foreground") {Source = this, Mode = BindingMode.OneWay});
label.SetBinding(FrameworkElement.MarginProperty, new Binding("Margin") {Source = this, Mode = BindingMode.OneWay});
}
}
Obejmuje cel własnym szablonem, dodając do niego etykietę:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ControlTemplate x:Key="HintBehaviorWrapper" TargetType="{x:Type ContentControl}">
<Grid>
<ContentPresenter Content="{TemplateBinding Content}" />
<Label x:Name="PART_HintLabel" IsHitTestVisible="False" Padding="0" />
</Grid>
</ControlTemplate>
</ResourceDictionary>
Aby go użyć, po prostu dodaj go jako zachowanie i powiąż swoje wartości (w moim przypadku dodam go w ControlTemplate, stąd wiązanie):
<ContentControl>
<i:Interaction.Behaviors>
<behaviors:HintBehavior Value="{Binding Property, RelativeSource={RelativeSource TemplatedParent}}"
Hint="{Binding Hint, RelativeSource={RelativeSource TemplatedParent}}" />
</i:Interaction.Behaviors>
<TextBox ... />
</ContentControl>
Chciałbym uzyskać informację zwrotną, jeśli jest to uważane za czyste rozwiązanie. Nie wymaga statycznych słowników i dlatego nie ma wycieków pamięci.