一个简单的例子看明白 async await Task

测试代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using Utils;

namespace test
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        /// <summary>
        /// 执行任务
        /// </summary>
        public string DoWork(string str)
        {
            Thread.Sleep(3000); //模拟延迟 比如网络请求 用了3000毫秒
            return "输出：" + str;
        }

        /// <summary>
        /// 执行任务
        /// </summary>
        public Task<string> DoWorkByTask(string str)
        {
            return Task.Run(() =>
            {
                Thread.Sleep(3000); //模拟延迟 比如网络请求 用了3000毫秒
                return "输出：" + str;
            });
        }

        /// <summary>
        /// 测试1
        /// </summary>
        private async void button1_Click(object sender, EventArgs e)
        {
            LogTimeUtil logTime = new LogTimeUtil();

            var t1 = DoWorkByTask("测试值1");

            var t2 = DoWorkByTask("测试值2");

            string r1 = await t1;

            textBox1.AppendText(r1 + "
");

            string r2 = await t2;

            textBox1.AppendText(r2 + "
");

            logTime.LogTime("耗时", textBox1);
        }

        /// <summary>
        /// 测试2 
        /// 
        /// 等效于 测试1
        /// </summary>
        private void button2_Click(object sender, EventArgs e)
        {
            Task.Run(() => //如果不加Task.Run，界面会卡
            {
                LogTimeUtil logTime = new LogTimeUtil();

                Task<string> t1 = Task.Run<string>(() => { return DoWork("测试值1"); });
                Task<string> t2 = Task.Run<string>(() => { return DoWork("测试值2"); });

                Task.WaitAll(t1, t2);

                this.Invoke(new Action(() => //线程中修改控件数据要使用Invoke
                {
                    textBox1.AppendText(t1.Result + "
");
                    textBox1.AppendText(t2.Result + "
");
                }));

                logTime.LogTime("耗时", textBox1);
            });
        }

        /// <summary>
        /// 测试3 
        /// </summary>
        private async void button3_Click(object sender, EventArgs e)
        {
            LogTimeUtil logTime = new LogTimeUtil();

            var r1 = await DoWorkByTask("测试值1");

            textBox1.AppendText(r1 + "
");

            var r2 = await DoWorkByTask("测试值2");

            textBox1.AppendText(r2 + "
");

            logTime.LogTime("耗时", textBox1);
        }

        /// <summary>
        /// 测试4
        /// 
        /// 等效于 测试3
        /// </summary>
        private void button4_Click(object sender, EventArgs e)
        {
            Task.Run(() => //如果不加Task.Run，界面会卡
            {
                LogTimeUtil logTime = new LogTimeUtil();

                Task<string> t1 = Task.Run<string>(() => { return DoWork("测试值1"); });
                t1.Wait();
                this.Invoke(new Action(() => //线程中修改控件数据要使用Invoke
                {
                    textBox1.AppendText(t1.Result + "
");
                }));

                Task<string> t2 = Task.Run<string>(() => { return DoWork("测试值2"); });
                t2.Wait();
                this.Invoke(new Action(() => //线程中修改控件数据要使用Invoke
                {
                    textBox1.AppendText(t2.Result + "
");
                }));

                logTime.LogTime("耗时", textBox1);
            });
        }

    }
}

测试输出：

附 LogTimeUtil.cs：

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

namespace Utils
{
    /// <summary>
    /// 记录耗时
    /// </summary>
    public class LogTimeUtil
    {
        private DateTime _lastTime;

        public LogTimeUtil()
        {
            _lastTime = DateTime.Now;
        }

        /// <summary>
        /// 记录耗时
        /// </summary>
        public void LogTime(string msg)
        {
            double d = DateTime.Now.Subtract(_lastTime).TotalSeconds;
            LogUtil.Log(msg + "，耗时：" + d.ToString("0.000") + " 秒");
        }

        /// <summary>
        /// 记录耗时
        /// </summary>
        public void LogTime(string msg, TextBox txt)
        {
            double d = DateTime.Now.Subtract(_lastTime).TotalSeconds;
            msg = msg + "，耗时：" + d.ToString("0.000") + " 秒
";
            if (txt.InvokeRequired)
            {
                txt.Invoke(new Action(() =>
                {
                    txt.AppendText(msg);
                }));
            }
            else
            {
                txt.AppendText(msg);
            }
        }
    }
}