了解.NET 通用主机-编程知识

了解.NET 通用主机

写在前面

.NET 通用主机负责应用启动和生存期管理，主机是封装应用资源和生存期功能的对象，通用主机可用于其他类型的 .NET 应用程序，如控制台应用；.NET 通用主机基于类库Microsoft.Extensions.Hosting 来实现，本文记录如何使用.NET 辅助角色服务模板来创建通用主机。

代码实现

以下示例是注册 IHostApplicationLifetime 事件的 IHostedService 实现

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;public sealed class ExampleHostedService : IHostedService
{private readonly ILogger _logger;private IHostApplicationLifetime _applicationLifetime;public ExampleHostedService(ILogger<ExampleHostedService> logger,IHostApplicationLifetime appLifetime){_logger = logger;appLifetime.ApplicationStarted.Register(OnStarted);appLifetime.ApplicationStopping.Register(OnStopping);appLifetime.ApplicationStopped.Register(OnStopped);_applicationLifetime = appLifetime;}public Task StartAsync(CancellationToken cancellationToken){_logger.LogInformation("1. StartAsync has been called.");return Task.CompletedTask;}public Task StopAsync(CancellationToken cancellationToken){_logger.LogInformation("4. StopAsync has been called.");return Task.CompletedTask;}private async void OnStarted(){_logger.LogInformation("2. OnStarted has been called.");var count = 0;var task = Task.Run(() =>{while (true){count++;Console.WriteLine("running...");Thread.Sleep(1000);if (count == 5){_applicationLifetime.StopApplication();}}});}private void OnStopping(){_logger.LogInformation("3. OnStopping has been called.");}private void OnStopped(){_logger.LogInformation("5. OnStopped has been called.");}
}

修改辅助角色服务模板以添加 ExampleHostedService 实现

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
builder.Services.AddHostedService<ExampleHostedService>();IHost host = builder.Build();
host.Run();Environment.Exit(0);