ASP.NETCORE 启动事件的两种捕获方式--可以自定义预加载和卸载相关任务

1、新建项目ASP.NETCORE项目ASP.NETCORETest

2、在Startup.cs中添加如下，包括2种方式捕获启动和停止事件接口，其中FirstStartService : IHostedService ，SecondStartService : IHostedService，IHostedService是Microsoft.Extensions.Hosting下的IHostedService，该接口包括StartAsync，StopAsync，主应用程序启动和停止的接口

第一种方式如下

public void ConfigureServices(IServiceCollection services)
{
services.AddRazorPages();
//应用程序启动起处理的的任务
services.AddHostedService<FirstStartService>();
services.AddHostedService<SecondStartService>();
}

FirstStartService代码

using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace ASP.NETCORETest
{
    public class FirstStartService : IHostedService
    {
        public async Task StartAsync(CancellationToken cancellationToken)
        {
            await Task.Run(() => { Console.WriteLine("FirstStartService......StartAsync"); }, cancellationToken);
        }

        public async Task StopAsync(CancellationToken cancellationToken)
        {
            await Task.Run(() => { Console.WriteLine("FirstStartService......StopAsync"); }, cancellationToken);
        }
    }
}

SecondStartService代码

using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace ASP.NETCORETest
{
    public class SecondStartService : IHostedService
    {
        public async Task StartAsync(CancellationToken cancellationToken)
        {
            await Task.Run(() => { Console.WriteLine("SecondStartService......"); }, cancellationToken);
        }

        public async Task StopAsync(CancellationToken cancellationToken)
        {
            await Task.Run(() => { Console.WriteLine("SecondStartService......StopAsync"); }, cancellationToken);
        }
    }
}

第二种方式是使用IHostApplicationLifetime，该接口可以捕获lHost的启动和停事件，

第二种方式如下

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IHostApplicationLifetime lifetime)
        {
            //IHostApplicationLifetime 除了程序进入点外，Host的启动和停止，ASP.NET Core不像ASP.NET MVC用继承的方式捕捉启动及停止事件，
            //而是透过Startup.Configure注入IHostApplicationLifetime来补捉Application启动停止事件
            lifetime.ApplicationStarted.Register(async () => await Task.Run(() => Console.WriteLine("IHostApplicationLifetime......Started")));
            lifetime.ApplicationStopping.Register(async () => await Task.Run(() => Console.WriteLine("IHostApplicationLifetime......Stopping")));
            lifetime.ApplicationStopped.Register(async () => await Task.Run(() => Console.WriteLine("IHostApplicationLifetime......Stopped")));

            var tt = new System.Threading.Thread(new System.Threading.ParameterizedThreadStart(a => {
                System.Threading.Thread.Sleep(TimeSpan.FromSeconds(10));
                Console.WriteLine("IHostApplicationLifetime......Stopp---------ing");
                lifetime.StopApplication();
            })) ;
            tt.Start();
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
            }

            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapRazorPages();
            });
        }

Program.cs中主方法如下：

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace ASP.NETCORETest
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}