取消退出流程控制方法

在自动化设备动作流程中，人为任意想取消当前动作，常见方法是使用全局变量，实时检测变量决定退出。这里介绍一个System.Threading空间下的 CancellationTokenSource类，他可以设置超时，设置信息等封装

基本使用超时和手动设置退出

CancellationTokenSource：用于控制和生成CancellationToken

CancellationToken:取消令牌,可以注册取消回调等操作

1、先实例化CancellationTokenSource

2、注册取消回调

3、启动一个Task，模拟耗时操作

4.调用CancellationTokenSource的CancelAfter方法,表示多少毫秒后取消,也可使用Cancel方法立即取消

5、IsCancellationRequested属性判断任务是否取消,没取消则一直输出i

抛出异常退出

以下举例 async await的异步使用,用到CancellationToken来取消任务，并手动设置抛异常传达信息

[HttpGet]public async Task<IActionResult> CancelDownLoad(CancellationToken cancellationToken){try{var _client = _httpClient.CreateClient("bigDownLoad");_client.DefaultRequestHeaders.Range = new RangeHeaderValue(0, 1024 * 1024 * 50);await Task.Delay(1000);if (!cancellationToken.IsCancellationRequested){var resp = await _client.GetAsync("http://du.cainiaoxt.cn/dd.php/windows_7_ultimate_x64_2023.iso",cancellationToken);if (resp.StatusCode != System.Net.HttpStatusCode.OK){string chunkFileFolder = @"D:\";string bigFileName = chunkFileFolder + @"\bigFile" + new Random().Next(0, 10);using (FileStream fs = new FileStream(bigFileName, FileMode.Create)){var respStream = await resp.Content.ReadAsStreamAsync();await respStream.CopyToAsync(fs);await respStream.FlushAsync();}}return Ok();}else{  // 设置抛异常退出cancellationToken.ThrowIfCancellationRequested();return BadRequest("下载任务取消!");}}catch (OperationCanceledException ex){Console.WriteLine("下载任务取消!"+ex.Message);return BadRequest("下载任务取消!");}}

关联退出

另外可以设置退出链接，多个关联全部退出

// See https://aka.ms/new-console-template for more information
CancellationTokenSource cts=new CancellationTokenSource();
cts.Token.Register(() => { Console.WriteLine("任务1已停止"); });CancellationTokenSource cts2 = new CancellationTokenSource();
cts2.Token.Register(() => { Console.WriteLine("任务2已停止"); });CancellationTokenSource cts3 = new CancellationTokenSource();
cts3.Token.Register(() => { Console.WriteLine("任务3已停止"); });
var linkTokenSource=CancellationTokenSource.CreateLinkedTokenSource(cts.Token, cts2.Token, cts3.Token);linkTokenSource.Token.Register(() => { Console.WriteLine("关联token取消"); });
Task.Run(() =>
{int i = 1;while (!cts.IsCancellationRequested){i++;Console.WriteLine("任务1："+i);Task.Delay(500).Wait();}});Task.Run(() =>
{int i = 1;while (!cts2.IsCancellationRequested){i++;Console.WriteLine("任务2："+i);Task.Delay(500).Wait();}});Task.Run(() =>
{int i = 1;while (!cts3.IsCancellationRequested){i++;Console.WriteLine("任务3："+i);Task.Delay(500).Wait();}});Task.Run(() =>
{int i = 1;while (!linkTokenSource.IsCancellationRequested){i++;Console.WriteLine("关联token任务：" + i);Task.Delay(500).Wait();}});var key=Console.ReadKey();
if(key.Key==ConsoleKey.A)
{cts.Cancel();
}
Console.ReadLine();