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POConverter with Dependency Properties
 

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  1. POConverter with Dependency Properties
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    <p>I have problems implementing a custom DependencyObject: </p> <p>I need a converter which sets or unsets a enum flag in a bound property. Therefore I created a IValueConverter derieved from FrameworkElement with two DependencyProperties: Flag (the flag which is set/unset by the converter) and Flags (the value/property to modify). The parent UserControl (Name = EnumerationEditor) provides the property to which the converter is bound.</p> <p>A ListBox generates CheckBoxes and the converter instances which are used to modify the property via a DataTemplate. Each CheckBox/converter instance is used for one flag. I use the following XAML code:</p> <pre class="lang-xml prettyprint-override"><code>&lt;ListBox Name="Values" SelectionMode="Extended" BorderThickness="1" BorderBrush="Black" Padding="5"&gt; &lt;ListBox.ItemTemplate&gt; &lt;DataTemplate DataType="{x:Type system:Enum}"&gt; &lt;DataTemplate.Resources&gt; &lt;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}"/&gt; &lt;converters:EnumerationConverter x:Key="EnumerationConverter" x:Shared="False" Flag="{Binding}" Flags="{Binding Path=Value, ElementName=EnumerationEditor}"/&gt; &lt;/DataTemplate.Resources&gt; &lt;StackPanel Orientation="Horizontal"&gt; &lt;CheckBox Content="{Binding}" IsChecked="{Binding Path=Value, ElementName=EnumerationEditor, Converter={StaticResource EnumerationConverter}}"/&gt; &lt;ContentPresenter Content="{StaticResource myTestResource}"/&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/ListBox.ItemTemplate&gt; &lt;/ListBox&gt; </code></pre> <p><strong>The strange thing: The Label works fine - but the converter does not.</strong> I get the error:</p> <blockquote> <p>System.Windows.Data Error: 4 : Cannot find source for binding with reference 'ElementName=EnumerationEditor'. BindingExpression:Path=Value; DataItem=null; target element is 'EnumerationConverter' (Name=''); target property is 'Flags' (type 'Enum')</p> </blockquote> <p>I don't understand why, the binding is basically the same...</p> <p>Here is the code for the converter:</p> <pre><code>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); } } /// &lt;summary&gt; /// Dependency property for Flag. /// &lt;/summary&gt; 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); } } /// &lt;summary&gt; /// Dependency property for Flags. /// &lt;/summary&gt; public static readonly DependencyProperty FlagsProperty = DependencyProperty.Register("Flags", typeof(Enum), typeof(EnumerationConverter)); #endregion } </code></pre>
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    1. COis EnumerationEditor part of your usercontrol, you have posted only the listbox
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    2. CO@anivas: Yes, it is the UserControl itself. It has a dependecy Property called Value of type Enum. But as you can see in the snippets, I use the exact same binding for Label.ToolTip as for the Converter. The Label.ToolTip works - it displays the correct value. But the converter produces the error.
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    3. COConverters will not be part of the visual tree, thats why it couldnt find it. what are you trying to do?
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