MainWindow.xaml.cs:


    using System.Collections.ObjectModel;
    using System.Windows;
    
    namespace ListViewNotShowData
    {
        public partial class MainWindow : Window
        {
            public MainWindow()
            {
                InitializeComponent();
            }
           
        }
        public class ViewModel
        {
            public ObservableCollection<PLC> PLCs { get; set; } = new ObservableCollection<PLC>();
            public ObservableCollection<Tag> Tags { get; set; }
            public ViewModel()
            {
                Tags = new ObservableCollection<Tag>() ;
                Tags.Add(new Tag() { Name="name1",Value= 1 });
                PLCs.Add(new PLC() { Name = "plc3", Tags = Tags });
            }
        }
        public class PLC
        {
            public string Name { get; set; }
            public ObservableCollection<Tag> Tags { get; set; }
            public PLC() { }
            public PLC(string name)
            {
                Name = name;
                Tags = new ObservableCollection<Tag>();
            }
        }
        public class Tag
        {
            public Tag()
            {
            }
            public Tag(string name, int value)
            {
                Name = name;
                Value = value;
            }
            public string Name { get; set; }
            public int Value { get; set; }
        }
    }