<Window x:Class="WpfApplication4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Border Background="Black">
            <Border.Triggers>
                <EventTrigger RoutedEvent="Loaded">
                    <BeginStoryboard>
                        <Storyboard>
                            <ColorAnimation Storyboard.TargetProperty="Background.Color" To="DarkRed" AutoReverse="True" RepeatBehavior="Forever" />
                        </Storyboard>
                    </BeginStoryboard>
                </EventTrigger>
            </Border.Triggers>
        </Border>
        <Button VerticalAlignment="Center" HorizontalAlignment="Center" Content="Вернуть ID потока" Click="Button_Click_1"/>
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication4
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            MessageBox.Show(string.Format("{0}", Thread.CurrentThread.Name));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Threading;

namespace WpfApplication4
{
    static class Program
    {
        private static List<Thread> _uiThreads;

        public static void Main()
        {
            _uiThreads = new List<Thread>{
                new Thread(UiThread) { ApartmentState = ApartmentState.STA, Name = "UI1 THREAD" },
                new Thread(UiThread) { ApartmentState = ApartmentState.STA, Name = "UI2 THREAD" },
                new Thread(UiThread) { ApartmentState = ApartmentState.STA, Name = "UI3 THREAD" }
            };

            _uiThreads.ForEach(t => { t.Start(); });
        }

        public static void UiThread()
        {
            var mainWnd = new MainWindow();
            mainWnd.Closed += mainWnd_Closed;
            mainWnd.Show();

            Dispatcher.Run();
        }

        static void mainWnd_Closed(object sender, EventArgs e)
        {
            (sender as MainWindow).Closed -= mainWnd_Closed;

            Dispatcher.ExitAllFrames();
        }
    }
}