How to bind to Popup.IsOpen to Validation.HasError in code

I have a Textbox which is bound to my data object. If the validation fails I would like to show a popup which contains the error message. In XAML this works fine. I'm using the following XAML:

<TextBox Height="23" Margin="54,12,104,0" Name="textBox1" 
VerticalAlignment="Top" Text="{Binding Value, ValidatesOnExceptions=True, UpdateSourceTrigger=PropertyChanged}"></TextBox>

        <Popup Name="myPopup" PlacementTarget="{Binding ElementName=textBox1}"
                       IsOpen="{Binding ElementName=textBox1, Path=(Validation.HasError), Mode=OneWay}"
                       >
            <TextBlock Name="myPopupText" Background="LightBlue" Foreground="Blue">
                        The value is invalid
            </TextBlock>
        </Popup>

My problem is that I have to create the popup and binding in code and I cannot get it to work. I have tried several different options. I also used dummy converter just to see whether the binding works at all. It seems that the binding works when I create it (it gets the initial value) but after that nothing happens. I can see that the Validation.HasError updates correctly (TextBox's border turns red), but that's it. My dummy converter is not called. Here is the code I'm using:

    Popup popup = new Popup();
    popup.Name = "somepopup";
    // Source is the textbox which is bound to the data object
    popup.PlacementTarget = source;
    popup.Placement = PlacementMode.Bottom;
    TextBlock txtblock = new TextBlock();
    txtblock.Background = Brushes.LightBlue;
    txtblock.Foreground = Brushes.Blue;
    txtblock.Text = "this is the error message";
    popup.Child = txtblock;

    Binding is_open_binding = new Binding("(Validation.HasError)");
    is_open_binding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
    is_open_binding.Source = source;
    is_open_binding.Mode = BindingMode.OneWay;
    is_open_binding.NotifyOnValidationError = true;
    is_open_binding.ValidatesOnExceptions = true;
    is_open_binding.Converter = new TempValueConverter();
    popup.SetBinding(Popup.IsOpenProperty, is_open_binding);

From stackoverflow

• Just did a simple test and it worked fine. Here is my XAML:

  <Window x:Name="_root" x:Class="WpfApplication1.Window1"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="Window1" Height="300" Width="300">
      <StackPanel>
       <TextBox x:Name="_textBox">
        <TextBox.Text>
         <Binding Path="Text" ElementName="_root" UpdateSourceTrigger="PropertyChanged">
          <Binding.ValidationRules>
           <ExceptionValidationRule/>
          </Binding.ValidationRules>
         </Binding>
        </TextBox.Text>
       </TextBox>
       <!--<Popup x:Name="_popup" IsOpen="{Binding (Validation.HasError), ElementName=_textBox, Mode=OneWay}">-->
       <Popup x:Name="_popup">
        <Border BorderThickness="1" BorderBrush="Black" Background="White">
         <TextBlock>Here I am.</TextBlock>
        </Border>
       </Popup>
      </StackPanel>
  </Window>
  

  And here is the code-behind:

  using System;
  using System.Windows;
  using System.Windows.Controls.Primitives;
  using System.Windows.Data;
  
  namespace WpfApplication1
  {
      public partial class Window1 : Window
      {
       public string Text
       {
        get { return "Text"; }
        set { if (value != "Text") throw new InvalidOperationException("Bla"); }
       }
  
       public Window1()
       {
        InitializeComponent();
  
        var binding = new Binding("(Validation.HasError)");
        binding.Source = _textBox;
        binding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
        binding.Mode = BindingMode.OneWay;
        binding.NotifyOnValidationError = true;
        binding.ValidatesOnExceptions = true;
        //binding.Converter = new TempValueConverter();
        _popup.SetBinding(Popup.IsOpenProperty, binding);
       }
  
       private sealed class TempValueConverter : IValueConverter
       {
        #region IValueConverter Members
  
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
         throw new NotImplementedException();
        }
  
        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
         throw new NotImplementedException();
        }
  
        #endregion
       }
      }
  }
  

  HTH, Kent

• I also made a simple solution and copied in your code and it ran just fine. Kent had his Popup declared in XAML, but I used your exact code for creating the Popup and setting the binding, so that difference shouldn't be the cause of the problem for you.

  I am wondering if you could post where your source variable is coming from. You don't show that and I am wondering if it is what you think it is.

  Another thing you might posibly try is keeping a reference to the popup around incase it is being garbage collected. I believe this could be possible as if I recall correctly the binding uses a week event handler for change notification so their wouldn't be any lasting link to the Popup instance. I think this is unlikely however, but might be worth a shot.

  FYI the code I used to test this is as follows.

  XAML file:

  <Window x:Class="PopupOpenBindingTest.Window1"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="Window1"
      Height="300"
      Width="300">
  <Grid>
      <TextBox Height="23"
               Margin="54,12,104,0"
               Name="textBox1"
               VerticalAlignment="Top"
               Text="{Binding Text, ValidatesOnExceptions=True, UpdateSourceTrigger=PropertyChanged}" />
  </Grid></Window>
  

  Code-behind.

  public partial class Window1 : Window
  {
      public Window1()
      {
          InitializeComponent();
  
          DataContext = new DataObjectTest();
          this.Loaded += new RoutedEventHandler(Window1_Loaded);
      }
  
      void Window1_Loaded(object sender, RoutedEventArgs e)
      {
          TextBox source = textBox1;
  
          Popup popup = new Popup(); 
          popup.Name = "somepopup";
          popup.PlacementTarget = source; 
          popup.Placement = PlacementMode.Bottom; 
          TextBlock txtblock = new TextBlock(); 
          txtblock.Background = Brushes.LightBlue; 
          txtblock.Foreground = Brushes.Blue; 
          txtblock.Text = "this is the error message"; 
          popup.Child = txtblock;
          Binding is_open_binding = new Binding("(Validation.HasError)");// { Path = new PropertyPath(Validation.HasErrorProperty) }; 
          is_open_binding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged; 
          is_open_binding.Source = source; 
          is_open_binding.Mode = BindingMode.OneWay; 
          is_open_binding.NotifyOnValidationError = true; 
          is_open_binding.ValidatesOnExceptions = true; 
          //is_open_binding.Converter = new TempValueConverter(); 
          popup.SetBinding(Popup.IsOpenProperty, is_open_binding);
      }
  
      public class DataObjectTest
      {
          private string _text = string.Empty;
  
          public string Text
          {
              get { return _text; }
              set
              {
                  if (value.Length > 5)
                      throw new InvalidOperationException("Blah blah blah");
  
                  _text = value;
              }
          }
      }