我在实现自定义 DependencyObject 时遇到问题:
我需要一个转换器来设置或取消设置绑定属性中的枚举标志。因此,我创建了一个从 FrameworkElement 派生的 IValueConverter,它具有两个 DependencyProperties:Flag(由转换器设置/取消设置的标志)和 Flags(要修改的值/属性)。父 UserControl(名称 = EnumerationEditor)提供转换器绑定到的属性。
ListBox 生成复选框和转换器实例,用于通过 DataTemplate 修改属性。每个复选框/转换器实例都用于一个标志。我使用以下 XAML 代码:
<ListBox Name="Values" SelectionMode="Extended" BorderThickness="1" BorderBrush="Black" Padding="5">
<ListBox.ItemTemplate>
<DataTemplate DataType="{x:Type system:Enum}">
<DataTemplate.Resources>
<Label x:Key="myTestResource" x:Shared="False"
Content="{Binding}"
ToolTip="{Binding Path=Value, ElementName=EnumerationEditor}"
Foreground="{Binding Path=Background, ElementName=EnumerationEditor}"
Background="{Binding Path=Foreground, ElementName=EnumerationEditor}"/>
<converters:EnumerationConverter x:Key="EnumerationConverter" x:Shared="False"
Flag="{Binding}"
Flags="{Binding Path=Value, ElementName=EnumerationEditor}"/>
</DataTemplate.Resources>
<StackPanel Orientation="Horizontal">
<CheckBox Content="{Binding}" IsChecked="{Binding Path=Value, ElementName=EnumerationEditor, Converter={StaticResource EnumerationConverter}}"/>
<ContentPresenter Content="{StaticResource myTestResource}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
奇怪的是:标签工作正常 - 但转换器却不行。我收到错误:
System.Windows.Data 错误:4:找不到引用“ElementName=EnumerationEditor”的绑定源。绑定表达式:路径=值;数据项=空;目标元素是“EnumerationConverter”(名称=“”);目标属性是“Flags”(类型“Enum”)
我不明白为什么,绑定基本上是一样的......
这是转换器的代码:
public class EnumerationConverter : FrameworkElement, IValueConverter
{
#region IValueConverter
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return false;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return Parity.Space;
}
#endregion
#region public Enum Flag { get; set; }
public Enum Flag
{
get { return (Enum)this.GetValue(EnumerationConverter.FlagProperty); }
set { this.SetValue(EnumerationConverter.FlagProperty, value); }
}
/// <summary>
/// Dependency property for Flag.
/// </summary>
public static readonly DependencyProperty FlagProperty = DependencyProperty.Register("Flag", typeof(Enum), typeof(EnumerationConverter));
#endregion
#region public Enum Flags { get; set; }
public Enum Flags
{
get { return (Enum)this.GetValue(EnumerationConverter.FlagsProperty); }
set { this.SetValue(EnumerationConverter.FlagsProperty, value); }
}
/// <summary>
/// Dependency property for Flags.
/// </summary>
public static readonly DependencyProperty FlagsProperty = DependencyProperty.Register("Flags", typeof(Enum), typeof(EnumerationConverter));
#endregion
}