WPF DataGrid conditional RowHeader problem - wpf

Question

I want to conditionally show different RowHeader contents in the WPF datagrid. E.g. My Model has two properties, Name and IsSuperHero. If the row represents a super-hero I want to show textbox with 'SH' in the row-header.
I am trying to achieve this using datatriggers as below. The problem is, the text-box is shown only on one row (the last matching row).
Below, I expect 'SH' to be shown against Superman and Batman but it shows up only against Batman. If I sort on Name column the records are sorted to 'Batman, John, Peter, Superman' and now the 'SH' header is shown against 'Superman' (that happens to be last matching record).
Am I missing something here?
public class UserModel
{
public String Name { get; set; }
public Boolean IsSuperHero { get; set; }
public UserModel (String name, Boolean issuperhero) { Name = name; IsSuperHero = issuperhero; }
}
public partial class MainWindow : Window
{
private void Window_Loaded (object sender, RoutedEventArgs e){
List<UserModel> list = new List<UserModel>();
list.Add(new UserModel("Peter", false));
list.Add(new UserModel("Superman", true));
list.Add(new UserModel("John", false));
list.Add(new UserModel("Batman", true));
myDataGrid.ItemsSource = list;
//Show Header 'SH' for Super Hero
TextBox txtBox = new TextBox();
txtBox.Text = "SH";
Style rowStyle = new Style();
DataTrigger dataTrigger = new DataTrigger();
dataTrigger.Binding = new Binding("IsSuperHero");
dataTrigger.Value = true;
Setter setter = new Setter(DataGridRow.HeaderProperty, txtBox);
dataTrigger.Setters.Add(setter);
rowStyle.Triggers.Add(dataTrigger);
myDataGrid.RowStyle = rowStyle;
}

Answer 1

The TextBox is only created once. You can add the TextBox as a resource in some dictionary and set x:IsShared to false, then reference it using the StaticResourceMarkupExtension, that way a new one will be created in every call.
(As x:Shared cannot be set in code this approach should be taken to XAML, i do not see any reason why one would want to do this in code in the first place)