为什么我的后台服务立即停止？

Question

我正在使用 .NET Core 2.2，并且我想运行长时间运行的后台任务（如旧的 Windows 服务）。我想使用Microsoft.Extensions.Hosting.BackgroundService（在Microsoft.Extensions.Hosting.Abstractions装配中）。

我的问题是我的服务立即启动和停止。我写了这个小样本来展示我所做的：

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Threading;
using System.Threading.Tasks;

namespace MyHostedService
{
    internal static class Program
    {
        private static void Main()
        {
            new HostBuilder()
                .ConfigureServices((hostContext, services) => { services.AddHostedService<MyService>(); })
                .Build()
                .RunAsync();
        }
    }
    public class MyService : BackgroundService
    {
        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            int count = 0;
            while (!stoppingToken.IsCancellationRequested)
            {
                Console.WriteLine($"Hit count: {++count}, IsCancellationRequested: {stoppingToken.IsCancellationRequested}");
                await Task.Delay(TimeSpan.FromSeconds(1));
            }
            Console.WriteLine($"IsCancellationRequested: {stoppingToken.IsCancellationRequested}");
            Console.WriteLine("The end.");
        }
    }
}

这是输出：

> Hit count: 1, IsCancellationRequested: False
Application started. Press Ctrl+C to shut down.
Hosting environment: Production
Content root path: C:\Users\(personnal path hidden)\MyHostedService\MyHostedService\bin\Debug\netcoreapp2.2\
> IsCancellationRequested: True
> The end.

C:\Program Files\dotnet\dotnet.exe (process 31088) exited with code 0.
To automatically close the console when debugging stops, enable Tools->Options->Debugging->Automatically close the console when debugging stops.
Press any key to close this window . . .

我保证，我没有按 Ctrl+C，也没有按退出键。

我错过了什么吗？您能否告诉我要更改哪些内容以确保该服务能够运行，直到我按 Ctrl+C 停止它为止？

我期望得到如下结果：

Application started. Press Ctrl+C to shut down.
Hosting environment: Production
Content root path: C:\Users\(personnal path hidden)\MyHostedService\MyHostedService\bin\Debug\netcoreapp2.2\
> Hit count: 1, IsCancellationRequested: False
> Hit count: 2, IsCancellationRequested: False
> Hit count: 3, IsCancellationRequested: False
> Hit count: 4, IsCancellationRequested: False
> Hit count: 5, IsCancellationRequested: False
> Hit count: 6, IsCancellationRequested: False
> Hit count: 7, IsCancellationRequested: False
> Hit count: 8, IsCancellationRequested: False
> Hit count: 9, IsCancellationRequested: False
> Hit count: 10, IsCancellationRequested: False
> Hit count: 11, IsCancellationRequested: False

...（现在我按 Ctrl+C ）...

> IsCancellationRequested: True
> The end.

C:\Program Files\dotnet\dotnet.exe (process 31088) exited with code 0.
To automatically close the console when debugging stops, enable Tools->Options->Debugging->Automatically close the console when debugging stops.
Press any key to close this window . . .

Answer 1

您异步运行它，因此一旦主函数到达末尾，应用程序就会退出。这就是请求取消的地方。尝试等待服务：

private async Task Main()
{
    await new HostBuilder()
        .ConfigureServices((hostContext, services) => { services.AddHostedService<MyService>(); })
        .Build()
        .RunAsync();
}