Summary  
This chapter covers moving blocking operations to background threads and marshaling updates back to the main thread to prevent UI freezes.

General domain of usage  
Responsive GUI applications

The base program is given on the <a 
href="https://github.com/Codefinity-Java/MAUIThreadingTask"
target="_blank"
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onmouseout="this.style.color='#d27204'">Github Repository</a>. Clone the repository to begin solving the task.

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  Statements related to UI updates are best to execute in the Main Thread.
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  <pre><code class="language-csharp">
using Microsoft.Maui.Controls.Shapes;
using System.Globalization;
using System.Net.Http;

namespace MauiApp1
{
    public class apiEvent
    {
        public delegate void apiEventHandler(object sender, apiEventArgs e);

        public event apiEventHandler? OnResponse;

        public void OnApiResponse(string content)
        {
            apiEventHandler? handler = OnResponse;

            if (handler != null)
            {
                handler(this, new apiEventArgs(content));
            }
        }
    }

    public class apiEventArgs : EventArgs
    {
        public string Link { get; }

        public apiEventArgs(string content)
        {
            this.Link = content;
        }
    }

    public partial class MainPage : ContentPage
    {
        public apiEvent apiService = new apiEvent();

        Thread? mainTimer;
        Thread? getRequestThread;
        long ticks;

        public MainPage()
        {
            InitializeComponent();

            getImageButton.Clicked += GetImage;
            apiService.OnResponse += SetImage;

            ticks = 0;
            mainTimer = new Thread(new ThreadStart(timerUpdate));
            mainTimer.Start();
        }

        public void timerUpdate()
        {
            while (true)
            {
                ticks++;
                Thread.Sleep(50);
                MainThread.BeginInvokeOnMainThread(() => {
                    timerLabel.Text = $"Tick Count: {ticks}";
                });
            }
        }

        private void SetImage(object? sender, apiEventArgs e)
        {
            MainThread.BeginInvokeOnMainThread(() =>
            {
                mainImage.Source = e.Link;
            });
        }

        private void GetImage(object? sender, EventArgs e)
        {
            if (getRequestThread != null && !getRequestThread.IsAlive)
                getRequestThread = null;

            if (getRequestThread == null)
            {
                getRequestThread = new Thread(new ThreadStart(GetRequest));
                getRequestThread.Start();
            }
        }

        private void GetRequest()
        {
            string apiUrl = "https://random.imagecdn.app/v1/image";

            using (HttpClient client = new HttpClient())
            {
                HttpResponseMessage response = client.GetAsync(apiUrl).Result;

                if (response.IsSuccessStatusCode)
                {
                    string content = response.Content.ReadAsStringAsync().Result;
                    apiService.OnApiResponse(content);
                }
            }
        }
    }
}    
      </code></pre>
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Dans ce cours, nous apprendrons certains concepts avancés de C# ainsi que MAUI, qui est une bibliothèque de développement d'applications. Nous apprendrons à créer des applications GUI intéressantes tout en les gardant rapides et réactives en utilisant des techniques comme le Threading. Nous créerons des applications qui interagiront avec les entrées utilisateur et les API, et en dehors de cela, nous couvrirons certains concepts importants de C# comme la Réflexion et les Génériques. Ce cours améliorera davantage nos compétences en programmation et nous donnera une base solide pour avancer vers le développement Web.

In this course, we will learn about some advanced C# concepts along with MAUI, which is an application development library. We will learn how to create some interesting GUI applications while keeping them quick and responsive using techniques like Threading. We will make applications that will interact user input and APIs, and apart from that, we will cover some important C# concepts like Reflection and Generics. This course will further improve our programming skills and will give us a strong foundation to move forward towards Web Development.

Tâche - Prévenir les Blocages de Programme en Utilisant le Threading

Description de la tâche