如果我们想要在Web Api服务中创建一个定制任务后台一直刷新执行某些操作，那么我们可以继承abstract抽象类HostedService，具体操作如下：
BackgroundService.cs源代码，这个源代码我可以自己写一个也可以直接继承。
/// <summary>
/// 自定义BackgroundService
/// </summary>
public abstract class BackgroundService : IHostedService, IDisposable
{#pragma warning disable CS8625 // 禁用CS8625警告private Task _executingTask = null;private readonly CancellationTokenSource _stoppingCts = new CancellationTokenSource();#pragma warning restore CS8625 // 恢复CS8625警告/// <summary>/// This method is called when the <see cref="IHostedService"/> starts. The implementation should return a task that represents/// the lifetime of the long running operation(s) being performed./// </summary>/// <param name="stoppingToken">Triggered when <see cref="IHostedService.StopAsync(CancellationToken)"/> is called.</param>/// <returns>A <see cref="Task"/> that represents the long running operations.</returns>protected abstract Task ExecuteAsync(CancellationToken stoppingToken);/// <summary>/// Triggered when the application host is ready to start the service./// </summary>/// <param name="cancellationToken">Indicates that the start process has been aborted.</param>public virtual Task StartAsync(CancellationToken cancellationToken){// Store the task we're executing_executingTask = ExecuteAsync(_stoppingCts.Token);// If the task is completed then return it, this will bubble cancellation and failure to the callerif (_executingTask.IsCompleted){return _executingTask;}// Otherwise it's runningreturn Task.CompletedTask;}/// <summary>/// Triggered when the application host is performing a graceful shutdown./// </summary>/// <param name="cancellationToken">Indicates that the shutdown process should no longer be graceful.</param>public virtual async Task StopAsync(CancellationToken cancellationToken){// Stop called without startif (_executingTask == null){return;}try{// Signal cancellation to the executing method_stoppingCts.Cancel();}finally{// Wait until the task completes or the stop token triggersawait Task.WhenAny(_executingTask, Task.Delay(Timeout.Infinite, cancellationToken));}}public virtual void Dispose(){_stoppingCts.Cancel();}
}- 另外我们需要创建一个HostedService.cs后台任务服务类型用于继承BackgroundService.cs抽象类，HostedService.cs代码如下：
public class HostedService : BackgroundService
{private readonly IServiceProvider _services;private readonly ILogger<HostedService> _logger;private readonly IHostApplicationLifetime _hostApplicationLifetime;public HostedService(IHostApplicationLifetime hostApplicationLifetime, ILogger<HostedService> logger, IServiceProvider services){_logger = logger;_services = services;_hostApplicationLifetime = hostApplicationLifetime;_hostApplicationLifetime.ApplicationStarted.Register(OnApplicationStarted);_hostApplicationLifetime.ApplicationStopping.Register(OnApplicationStopping);_hostApplicationLifetime.ApplicationStopped.Register(OnApplicationStopped);}private void OnApplicationStopped(){}private void OnApplicationStopping(){}private void OnApplicationStarted(){}public override void Dispose(){base.Dispose();}public override Task StartAsync(CancellationToken cancellationToken){return base.StartAsync(cancellationToken);}public override Task StopAsync(CancellationToken cancellationToken){_logger.LogWarning("服务停止……");return base.StopAsync(cancellationToken);}protected override Task ExecuteAsync(CancellationToken stoppingToken)
{_logger.LogInformation("服务启动……");new Task(() =>{while (!stoppingToken.IsCancellationRequested){// Do work hereConsole.WriteLine("Doing work...");Thread.Sleep(1000);}}, stoppingToken).Start();_logger.LogInformation("服务启动成功！");return Task.CompletedTask;
}}Program.cs中的配置如下：
namespace WebApplication26
{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>();});}public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }/// <summary>/// This method gets called by the runtime. Use this method to add services to the container./// </summary>/// <param name="services"></param>public void ConfigureServices(IServiceCollection services){services.AddControllers();services.AddEndpointsApiExplorer();services.AddSwaggerGen();services.AddMvc(options =>{options.EnableEndpointRouting = false; //禁用控制器名称的小写化//options.Filters.Add<RequestResultFilterAttribute>(); // 注册一个全局过滤器options.InputFormatters.Clear(); // 使用自定义的 JSON 解析选项//options.InputFormatters.Add(new CustomJsonInputFormatter());//options.Conventions.Add(new CustomRouteConvention()); // 添加一个自定义的路由约定});services.AddMemoryCache(); //配置缓存//注册定时任务执行类【https://blog.51cto.com/u_15437432/6172040?articleABtest=0】//添加主机服务services.AddHostedService<HostedService>(); //配置后台线程任务}/// <summary>/// This method gets called by the runtime. Use this method to configure the HTTP request pipeline./// </summary>/// <param name="app"></param>/// <param name="env"></param>public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()) //在开发环境中{app.UseDeveloperExceptionPage(); // 在开发环境中启用异常页面（可选）}else{app.UseExceptionHandler("/Home/Error");}app.UseSwagger(); // 启用Swagger中间件以生成和提供Swagger文档app.UseSwaggerUI(c => // 启用Swagger UI中间件以提供Swagger文档的UI界面{c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1.0"); // 指定Swagger文档的端点和名称});app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}主要是这段代码
services.AddHostedService<HostedService>();参考网址【https://blog.51cto.com/u_15437432/6172040?articleABtest=0】
