运行界面：

代码部分：

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

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
     public static  string resultWeight { get; set; } = "";
        Stopwatch stopwatch = new Stopwatch();
        public Form1()
        {
            InitializeComponent();

            Task.Run(RunThread);
        }

        private async Task RunThread()
        {
    
            while (true)
            {
                stopwatch.Restart();
                var t = await AsyncWeight();

                Console.WriteLine($"状态：{t}     时间：{stopwatch.ElapsedMilliseconds}");

                // Task.Delay(10).Wait();
                Thread.Sleep(10);
                Console.WriteLine($"状态：{t}     时间：{stopwatch.ElapsedMilliseconds}");
            }
        }

        /// <summary>
        /// Async修饰的方法    调用方法  var t=  await  AsyncWeight();
        /// </summary>
        /// <returns></returns>
        public static async Task<bool> AsyncWeight()
        {
            var result = await WasteWeight();
            return result;
        }
        /// <summary>
        /// 等待
        /// </summary>
        /// <returns></returns>
        private static async Task<bool> WasteWeight()
        {
            return await Task.Run(() =>
            {
                int i = 0;
                bool b = true;
                bool Return = false;
                while (b)
                {          
                    if (resultWeight.Length > 2)  //得到重量
                    {
                        b = false;
                        Return = true;
                    }
                    else if (i >= 400)   //等待40秒
                    {
                        b = false;
                        Return = false;
                    }
                    i++;
                    Console.WriteLine($"i={i}");
                    // Task.Delay(1000).Wait();
                    Thread.Sleep(1000);
                }
                return Return;
            });
        }

        private void button1_Click(object sender, EventArgs e)
        {
            resultWeight = string.Empty;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            resultWeight = "1234566778";
        }
    }
}