新建一个类，这里命名为Job

using Microsoft.Extensions.Hosting;using System;using System.IO;using System.Threading;using System.Threading.Tasks;namespace test.Jobs{    public class Job : BackgroundService    {        protected override async Task ExecuteAsync(CancellationToken stoppingToken)        {            while (!stoppingToken.IsCancellationRequested)            {                await new TaskFactory().StartNew(() =>                {                    try                    {                        //定时任务业务逻辑,比如:                        string value = DateTime.Now.ToString();                        StreamWriter sw = new StreamWriter(@"D:\1.txt", true);//true有新数据继续写,false后边的数据覆盖前边的                        sw.WriteLine("执行时间： " + value);                        sw.Flush();                        sw.Close();                        //满足某种条件执行 比如每天凌晨执行                        var time = DateTime.Now.ToString("HH:mm:ss");                        if ("00:01:00" == time)                        {                            //业务逻辑                             Console.WriteLine(DateTime.Now + ":进入这里了");                        }                    }                    catch (Exception exp)                    {                        //错误处理                    }                    //定时任务休眠                    Thread.Sleep(1 * 1000);                });            }        }    }}

最后在ConfigureServices里注册下

//定时任务的注入

services.AddTransient<Microsoft.Extensions.Hosting.IHostedService, Job>();

这样定时任务就OK了