Task.Delay 사용과 UI blcok 관계

Task_Delay_test1.cs

using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Task_Delay_test1
{
    public partial class Form1 : Form
    {
        Stopwatch stopwatch = new Stopwatch();

        public Form1()
        {
            InitializeComponent();

            Thread.CurrentThread.Name = "_mainUI_";
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Debug.WriteLine($"--- main UI -- {Thread.CurrentThread.ManagedThreadId}");
        }

        private async void button1_Click(object sender, EventArgs e)
        {

            Debug.WriteLine($"---Test1 -- START --");

            await this.Test1(); // await 없으면, 다음 코드 바로 실행됨.

            Debug.WriteLine($"---Test1 --- END ---");
        }

        private async Task Test1()
        {
            // no UI block & delay ok

            stopwatch.Reset();
            stopwatch.Start();

            await Task.Delay(3000);
            //Task.Delay(3000); // delay 없이, 다음 코드 실행됨

            stopwatch.Stop();
            Debug.WriteLine($"Test1() ; {Thread.CurrentThread.ManagedThreadId} ");
            Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Debug.WriteLine($"---Test2 -- START --");

            this.Test2(); // UI block 발생

            Debug.WriteLine($"---Test2 --- END ---");
        }

        private void Test2()
        {
            // UI block 발생, UI delay ok

            var t = Task.Run(async () =>
            {
                stopwatch.Reset();
                stopwatch.Start();

                await Task.Delay(5000);

                stopwatch.Stop();
                Debug.WriteLine($"Thread Id : {Thread.CurrentThread.ManagedThreadId}");
                Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");
            });

            t.Wait();

            Debug.WriteLine($"-----Test2-------");

        }

        private void button3_Click(object sender, EventArgs e)
        {
            Debug.WriteLine($"---Test3 -- START --");

            this.Test3(); //--- no UI block, no delay

            Debug.WriteLine($"---Test3 --- END ---");
        }

        private async void Test3()
        {
            //--- no UI block  #1 ---- but, await 해도 5초 delay 효과 없음. (no UI delay)

            await Task.Factory.StartNew(async () =>
            {
                stopwatch.Reset();
                stopwatch.Start();

                await Task.Delay(5000);

                stopwatch.Stop();
                Debug.WriteLine($"Thread Id : {Thread.CurrentThread.ManagedThreadId}");
                Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");
            });


            //--- no UI block  #2 ---- but, t.Wait() 해도 5초 delay 효과 없음. (no UI delay)

            //var t = Task.Factory.StartNew(async () =>
            //{
            //    stopwatch.Reset();
            //    stopwatch.Start();

            //    await Task.Delay(5000);

            //    stopwatch.Stop();
            //    Debug.WriteLine($"Thread Id : {Thread.CurrentThread.ManagedThreadId}");
            //    Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");
            //});
            //t.Wait();

            Debug.WriteLine($"-----Test3-------");

        }

        private async void button4_Click(object sender, EventArgs e)
        {
            Debug.WriteLine($"---Test4 -- START --");

            await this.Test4(); 

            Debug.WriteLine($"---Test4 --- END ---");
        }

        private async Task Test4()
        {
            // await --> no UI block
            // Wait() --> UI block 발생

            for (int i = 0; i < 10; i++)
            {
                stopwatch.Reset();
                stopwatch.Start();

                //Task.Delay(200);  // delay 없이, 다음 코드로 넘어감. -- no delay
                await Task.Delay(200);  // no UI block , UI delay ok
                //Task.Delay(200).Wait();   // UI block, UI delay ok

                stopwatch.Stop();
                Debug.WriteLine($"{i} ; {Thread.CurrentThread.ManagedThreadId}");
                Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");
            }
        }

        private async void button5_Click(object sender, EventArgs e)
        {
            Debug.WriteLine($"---Test5 -- START --");

            for (int i = 0; i < 10; i++)
            {
                stopwatch.Reset();
                stopwatch.Start();

                await this.Test5();  // await 없으면, delay 없음.

                stopwatch.Stop();
                Debug.WriteLine($"Thread Id : {Thread.CurrentThread.ManagedThreadId}");
                Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");
            }

            Debug.WriteLine($"---Test5 --- END ---");
        }

        // 호출시 await Test5() 로 해야지, delay 발생함.
        private async Task Test5()
        {
            await Task.Delay(500);  // no UI block , UI delay ok
            //Task.Delay(500).Wait();  // UI block, UI delay ok

        }

        private void button6_Click(object sender, EventArgs e)
        {
            Debug.WriteLine($"---Test6 -- START --");

            this.Test6();

            Debug.WriteLine($"---Test6 --- END ---");
        }

        private void Test6()
        {
            // UI block. delay ok 

            stopwatch.Reset();
            stopwatch.Start();

            Task.Delay(3000).GetAwaiter().GetResult();  // UI block, delay ok

            stopwatch.Stop();
            Debug.WriteLine($"Test6() ; {Thread.CurrentThread.ManagedThreadId}");
            Debug.WriteLine($"  elapsed time = {stopwatch.Elapsed.Seconds}초 {stopwatch.Elapsed.Milliseconds}");

        }


    }
}