this is a XAML interface game from Head First C# for an animal matching game, it introduces using the dispatch timer. Looking back on it, I don't understand at all what the = operator could be doing. Timer_Tick returns void, so it doesn't look like it's adding the evaluation. Is DispatcherTimer.Tick a method? Does the operator = make another method execute whenever the first method is called?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace MatchGame
{
    using System.Windows.Threading;
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        DispatcherTimer timer = new DispatcherTimer();
        int tenthsOfSecondsElapsed;
        int matchesFound;

        public MainWindow()
        {
            InitializeComponent();

            timer.Interval = TimeSpan.FromSeconds(.1);
            timer.Tick  = Timer_Tick;
            SetUpGame();
        }

        private void Timer_Tick(object sender, EventArgs e)
        {
            tenthsOfSecondsElapsed  ;
            timeTextBlock.Text = (tenthsOfSecondsElapsed / 10F).ToString("0.0s");
            if(matchesFound == 8)
            {
                timer.Stop();
                timeTextBlock.Text = timeTextBlock.Text   " - Play Again?";
            }
        }

        private void SetUpGame()
        {
            List<String> animalEmoji = new List<string>()
            {
                "🦊","🦊",
                "🐌","🐌",
                "🦓","🦓",
                "🐷","🐷",
                "🦒","🦒",
                "🦇","🦇",
                "🐧","🐧",
                "🐢","🐢",
            };
            Random random = new Random();
            foreach (TextBlock textBlock in mainGrid.Children.OfType<TextBlock>())
            {
                if(textBlock.Name != "timeTextBlock")
                {
                    textBlock.Visibility = Visibility.Visible;
                    int index = random.Next(animalEmoji.Count);
                    string nextEmoji = animalEmoji[index];
                    textBlock.Text = nextEmoji;
                    animalEmoji.RemoveAt(index);
                }
                timer.Start();
                tenthsOfSecondsElapsed = 0;
                matchesFound = 0;
            }
        }
        //track clicked box
        TextBlock lastBlockClicked;
        //track user state (first or second click)
        bool findingMatch = false;
        private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
        {
            /*
             * if it's the first in a pair being clicked, 
             *      keep track of which was clicked
             *      make the animal disappear
             * if it's the second one
             *      if it matches
             *          make it dissapear
             *      else
             *          make the first one reappear
             */
            TextBlock textBlock = sender as TextBlock;
            if (findingMatch == false)
            {
                textBlock.Visibility = Visibility.Hidden;
                lastBlockClicked = textBlock;
                findingMatch = true;
            }
            else if (textBlock.Text == lastBlockClicked.Text)
            {
                matchesFound  ;
                textBlock.Visibility = Visibility.Hidden;
                findingMatch = false;
            }
            else
            {
                lastBlockClicked.Visibility = Visibility.Visible;
                findingMatch = false;
            }
        }

        private void TimeTextBlock_MouseDown(object sender, MouseButtonEventArgs e)
        {
            //reset the game if all 8 matches found
            if (matchesFound == 8)
            {
                SetUpGame();
            }
        }
    }
}