C#线程暂停和继续操作 (Thread及Task) 多线程的异常如何捕捉， 多个线程返回结果合计 监视锁

多线程异常的捕捉：需要批量的等待: Task.WaitAll(tasklist.ToArray());

摘自：https://www.cnblogs.com/LcVong/p/12651599.html

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;

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

            Label.CheckForIllegalCrossThreadCalls = false;
        }
        
        ManualResetEvent ma = new ManualResetEvent(false);

        bool stop = false;

        //启动
        private void button1_Click(object sender, EventArgs e)
        {
            Thread thread = new Thread(Runtime);

            stop = false;

            ma.Set();// 信号打开，不阻塞当前线程

            thread.Start();
        }

        /// <summary>
        /// 线程
        /// </summary>
        void Runtime()
        {
            for (int i = 1; i <= 100; i++)
            {
                if (stop)
                {
                    return;
                }
                    
                ma.WaitOne();//根据是否收到信号判断是否阻塞当前线程

                textBox1.AppendText("计时 :" + i + "\r\n");

                Thread.Sleep(100);
            }
        }

        //暂停
        private void button2_Click(object sender, EventArgs e)
        {
            ma.Reset();//信号关闭阻塞当前线程

            textBox1.AppendText("暂停中 :\r\n");
        }

        //继续
        private void button3_Click(object sender, EventArgs e)
        {

            ma.Set();//信号打开，不阻塞当前线程

            textBox1.AppendText("继续计时 :\r\n");
        }

        //停止
        private void button4_Click(object sender, EventArgs e)
        {
            stop = true;

            textBox1.AppendText("停止计时 \r\n");
        }
    }
}

Task

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;

namespace WindowsFormsApp1
{
	public partial class Form4 : Form
	{
		private CancellationTokenSource cts = null;
		public Form4()
		{
			InitializeComponent();

			Label.CheckForIllegalCrossThreadCalls = false;
		}

		ManualResetEvent ma = new ManualResetEvent(true);

		bool stop = false;

		//启动
		private void button1_Click(object sender, EventArgs e)
		{
			//Thread thread = new Thread(Runtime);
			cts = new CancellationTokenSource();
			Task task = new Task(()=>Runtime(),cts.Token);

			stop = false;

			ma.Set();// 信号打开，不阻塞当前线程

			task.Start();
		}

		/// <summary>
		/// 线程
		/// </summary>
		async void Runtime()
		{
			for (int i = 1; i <= 100; i++)
			{
				if (stop)
				{
					return;
				}

				if (cts.IsCancellationRequested) return;

				ma.WaitOne();//根据是否收到信号判断是否阻塞当前线程

				textBox1.AppendText("计时 :" + i + "\r\n");

				//Thread.Sleep(100);
				await Task.Delay(100);
			}
		}

		//暂停
		private void button2_Click(object sender, EventArgs e)
		{
			ma.Reset();//信号关闭阻塞当前线程

			textBox1.AppendText("暂停中 :\r\n");
		}

		//继续
		private void button3_Click(object sender, EventArgs e)
		{

			ma.Set();//信号打开，不阻塞当前线程

			textBox1.AppendText("继续计时 :\r\n");
		}

		//停止
		private void button4_Click(object sender, EventArgs e)
		{
			//stop = true;
			cts.Cancel();
			textBox1.AppendText("停止计时 \r\n");

		}
	}
}

多个线程返回结果合计

Web线程等待 自己写异步线程

public partial class Form5 : Form
{
	public Form5()
	{
		InitializeComponent();
	}

	private async void button1_Click(object sender, EventArgs e)
	{
		textBox1.Text = "";
		#region 不够优雅
		//WebClient webClient = new WebClient();
		//Task.Run(() =>
		//{
		//	string html = webClient.DownloadString("https://www.youtube.com");  //如果不开线程会堵塞
		//	this.Invoke(new Action(() =>
		//	{
		//		textBox1.Text = html;   //.Substring(1,20);
		//	}));
		//}); 
		#endregion

		/*
		//(1) 卡界面
		HttpClient httpClient = new HttpClient();
		Task<string> t = httpClient.GetStringAsync("https://www.youtube.com");
		string html = t.Result;
		textBox1.Text = html;
		*/

		//(2) 不卡界面
		//HttpClient httpClient = new HttpClient();
		//Task<string> t = httpClient.GetStringAsync("https://www.youtube.com");
		//string html = await t;
		//textBox1.Text = html;

		/*
		//(3) 不卡界面 更简写, 优雅
		HttpClient httpClient = new HttpClient();
		string html =await httpClient.GetStringAsync("https://www.youtube.com");
		textBox1.Text = html;
		*/

		//下面试着写自己的异步函数
		string html =await  MyDownloadAsync("https://www.youtube.com");
		textBox1.Text = html;


	}

	/*
	private Task<string> MyDownloadAsync(string url)
	{
		WebClient webClient = new WebClient();
		return Task.Run(() =>
		{
			return webClient.DownloadString(url);
		});
	}
	*/
	//加了await, 不过好象没什么用 (多线程是实现异步的其中一种手段, 已经是多线程了, 应该是不用加await了)
	private async Task<string> MyDownloadAsync(string url)
	{
		WebClient webClient = new WebClient();
		return await Task.Run(() =>
		{
			return webClient.DownloadString(url);
		});
	}

}

范型与共享锁变量

region 监视锁:Lock 限制线程个数的一把锁

//为什么要用锁?在多线程中，尤其是静态资源的访问，必然会有竞争
private static int nums = 0;
private static object myLock = new object();1 个引用
static void Method12()
{
　　for (int i =0;i<5;i++)
　　{
　　　Task.Factory.StartNew(()=>
　　　{
　　　　TestMethod();
　　　});
　　}
}

static void TestMethod()
{
　　for (int i = 0;i< 100;i++)
　　{
　　　lock(myLock)
　　　{
　　　　nums++;
　　　　Console.WriteLine(nums):
　　　}
　　}
}
//Lock是Monitor语法糖，本质是解决资源的锁定问题
//我们锁住的资源一定是让线程可访问到的，所以不能是局部变量。
//锁住的资源千万不要是值类型。
//lock也不能锁住string类型。