Trigger on attached property of DataGridTextColumn - wpf

Question

I am trying to define a custom attached property on DataGridTextColumn and writing a DataTrigger against it in my xaml file. Here is how the attached property (FilterDisplayStyle) is defined in my class.
//Dependency Property whether Column Filter is combobox or textbox or editable combobox.
public static FrameworkPropertyMetadata inheritsMetaData =
new FrameworkPropertyMetadata(FilterDisplayTypeEnum.TextBoxOnly, FrameworkPropertyMetadataOptions.Inherits);
public static DependencyProperty FilterDisplayTypeProperty = DependencyProperty.RegisterAttached("FilterDisplayType",
typeof(FilterDisplayTypeEnum), typeof(DataGridColumn), inheritsMetaData);
public static FilterDisplayTypeEnum GetFilterDisplayType(DependencyObject target) {
if (target == null) { throw new ArgumentNullException("Invalid Parameter Element"); }
return (FilterDisplayTypeEnum)target.GetValue(FilterDisplayTypeProperty);
}
public static void SetFilterDisplayType(DependencyObject target, FilterDisplayTypeEnum value) {
if (target == null) { throw new ArgumentNullException("Invalid Parameter Element"); }
target.SetValue(FilterDisplayTypeProperty, value);
}
The above attached property's type is FilterDisplayTypeEnum which is defined as below.
public enum FilterDisplayTypeEnum {
TextBoxOnly,
NonEditableComboBox,
EditableComboBox
}
Here is how I set this property in DataGridTextColumn
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Id}" f:DataGridColumnExtensions.FilterDisplayType="NonEditableComboBox" />
....
</DataGrid.Columns>
Now I am trying to retrieve this property in using the following
<TextBox Text="{Binding Mode=OneWay, Path=FilterDisplayType, RelativeSource={RelativeSource AncestorType={x:Type DataGridTextColumn}}}"/>
But I don't get any text on my TextBox above.
Surprisingly, I have another attached property (this time attached to DataGrid instead) that works perfectly fine. The issue is only with DataGridTextColumn. Also, using WPF Inspector, I see there is no direct visual representation of DataGridTextColumn in the Visual Tree , so I was skeptical whether I could use FindAncestor way of binding on ancestor which is DataGridTextColumn. Can anyone help me out in this scenario. To Summarize, I can't access a custom attached property defined on DataGridTextColumn using FindAncestor type of Binding. Are there any alternatives to this?
regards,
Nirvan
Edit:
As per #Clemens suggestions, I changed the definition of the Attached Property to something like this. But I still can't access the attached property in my xaml.
Attached Property Definition:
public static DependencyProperty FilterDisplayTypeProperty = DependencyProperty.RegisterAttached("FilterDisplayType",
typeof(FilterDisplayTypeEnum), typeof(DataGridColumnExtensions), inheritsMetaData);
public static FilterDisplayTypeEnum GetFilterDisplayType(DataGridBoundColumn target) {
if (target == null) { throw new ArgumentNullException("Invalid Parameter target"); }
return (FilterDisplayTypeEnum)target.GetValue(FilterDisplayTypeProperty);
}
public static void SetFilterDisplayType(DataGridBoundColumn target, FilterDisplayTypeEnum value) {
if (target == null) { throw new ArgumentNullException("Invalid Parameter target"); }
target.SetValue(FilterDisplayTypeProperty, value);
}
I am still unable to access the property "FilterDisplayType" in my xaml code as given below
<TextBox Text="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGridTextColumn}}, Path=FilterDisplayType}"/>

Answer 1

The owner type must be the type that declares the property, here DataGridColumnExtensions:
public static DependencyProperty FilterDisplayTypeProperty =
DependencyProperty.RegisterAttached("FilterDisplayType",
typeof(FilterDisplayTypeEnum),
typeof(DataGridColumnExtensions), // here
inheritsMetaData);
This seems to be a common misunderstanding with attached properties. See also here.
And also note that the syntax for binding to an attached property is (Class.Property), so you would need to bind like this:
<TextBox
Text="{Binding Path=(DataGridColumnExtensions.FilterDisplayType)}"/>
And just another note: i haven't quite understood why the property inherits. As far as i can see you intend to set it explicitly on DataGridTextColumn objects.