using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Threading;
using System.Windows;
using System.Windows.Threading;

namespace WpfApp1
{
	public class TestViewModel
	{
		public ObservableCollection<string> Children { get; set; } = new ObservableCollection<string>();
	}

	public partial class MainWindow : Window
	{
		public TestViewModel ViewModel = new TestViewModel();
	
		public MainWindow()
		{
			InitializeComponent();

			DataContext = ViewModel;
			for (int i = 0; i < 4; i++)
			{
				new Thread(UpdateChildren) { IsBackground = true }.Start();
			}
		}

		private void UpdateChildren()
		{
			var mtid = Thread.CurrentThread.ManagedThreadId;
			Random random = new Random(mtid);
			int i = 0;
			var its = new List<string>();

			while (true)
			{
				if ((its.Count == 0) || (random.Next() % 2 == 0))
				{
					var it = $"{mtid}-{++i}";
					its.Add(it);

					Dispatcher.BeginInvoke((Action)delegate 
					{
						ViewModel.Children.Add(it);
					});
				}
				else
				{
					var index = random.Next(its.Count);
					var it = its[index];
					its.RemoveAt(index);

					Dispatcher.BeginInvoke((Action)delegate
					{
						ViewModel.Children.Remove(it);
					});
				}
				Thread.Sleep(random.Next(2));
			}
		}
	}
}