Binding a Trigger to a custom property in a UserControl

Question

I have a StackPanel with a handful of custom UserControls (MyUserControl). I'm trying to write a style trigger that will hide MyUserControls if their CustomObject dependency property has IsEnabled set to False.

For example, with no style...

<StackPanel>

    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[0]" />
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[1]" />
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[2]" />

</StackPanel>

And the gist of what I'm wanting to have happen, but I know this code isn't correct...

<StackPanel>
    <StackPanel.Resources>

        <Style TargetType="{x:Type controls:MyUserControl}">

            <Style.Triggers>

                 <DataTrigger Binding="{Binding Path=CustomObject.IsEnabled}" Value="False">

                    <Setter Property="Visibility" Value="Collapsed" />

                 </DataTrigger>

            </Style.Triggers>

        </Style>

    </StackPanel.Resources>

    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[0]" />
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[1]" />
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[2]" />

</StackPanel>

Answer 1

You can try below code to replace your DataTrigger:

<Style TargetType="{x:Type controls:MyUserControl}">  
            <Style.Triggers>  
                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=Self}, Path=(controls:MyUserControl.CustomObject)}" Value="False">  
                    <Setter Property="Visibility" Value="Collapsed" />  
                </DataTrigger>  
            </Style.Triggers>  
        </Style>  

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Answer 2

Hi,
with following demo I cannot reproduce your problem. Please, show more details.

XAML Main Window:

<Window x:Class="WpfApp1.MainWindow"  
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"  
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"  
        xmlns:local="clr-namespace:WpfApp1"  
        xmlns:controls="clr-namespace:WpfControlLibrary1;assembly=WpfControlLibrary1"  
        mc:Ignorable="d"  
        Title="MainWindow" Height="450" Width="800">  
  <Window.DataContext>  
    <local:ViewModel/>  
  </Window.DataContext>  
  <StackPanel>  
    <StackPanel.Resources>  
      <Style TargetType="{x:Type controls:MyUserControl}">  
        <Style.Triggers>  
          <DataTrigger Binding="{Binding Path=CustomObject.IsEnabled}" Value="False">  
            <Setter Property="Visibility" Value="Collapsed" />  
          </DataTrigger>  
        </Style.Triggers>  
      </Style>  
    </StackPanel.Resources>  
    <CheckBox Content="Visibility" IsChecked="{Binding Path=CustomObject.IsEnabled}"/>  
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[0]}" />  
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[1]}" />  
    <controls:MyUserControl CustomObject="{Binding Path=CustomObjects[2]}" />  
  </StackPanel>  
</Window>  

Classes:

using System.ComponentModel;  
using System.Runtime.CompilerServices;  
  
namespace WpfApp1  
{  
  class ViewModel  
  {  
    public Data1 CustomObject { get; set; } = new Data1();  
    public Data2 CustomObjects { get; set; } = new Data2();  
  }  
  
  public class Data1 : INotifyPropertyChanged  
  {  
    private bool _isEnabled = true;  
    public bool IsEnabled  
    {  
      get => this._isEnabled;  
      set { this._isEnabled = value; OnPropertyChanged(); }  
    }  
    public event PropertyChangedEventHandler PropertyChanged;  
    private void OnPropertyChanged([CallerMemberName] string propName = "") =>  
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));  
  }  
  public class Data2  
  {  
    private string[] arr = new string[3] { "test string 1", "test string  2", "test string    3" };  
  
    public string this[int i]  
    {  
      get { return arr[i]; }  
      set { arr[i] = value; }  
    }  
  }  
}  

XAML UserControl:

<UserControl x:Class="WpfControlLibrary1.MyUserControl"  
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"   
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"   
             xmlns:local="clr-namespace:WpfControlLibrary1"  
             mc:Ignorable="d"   
             d:DesignHeight="100" d:DesignWidth="800">  
  <Border x:Name="bo" BorderBrush="Red" BorderThickness="2" Margin="3" Width="100" HorizontalAlignment="Left">  
    <TextBlock Text="{Binding CustomObject}"/>  
  </Border>  
</UserControl>  

CodeBehind UserControl:

using System;  
using System.Windows;  
using System.Windows.Controls;  
  
namespace WpfControlLibrary1  
{  
  public partial class MyUserControl : UserControl  
  {  
    public MyUserControl()  
    {  
      InitializeComponent();  
      this.bo.DataContext = this;  
    }  
  
    public static readonly DependencyProperty CustomObjectProperty =  
        DependencyProperty.RegisterAttached("CustomObject", typeof(object),  
          typeof(MyUserControl), new PropertyMetadata(null));  
  
    public static object GetCustomObject(DependencyObject obj) => obj.GetValue(CustomObjectProperty);  
    public static void SetCustomObject(DependencyObject obj, Object value) => obj.SetValue(CustomObjectProperty, value);  
  }  
}  

Result: