如何为后台服务传递参数？

Question

如何为后台服务传递参数？

9

我了解了ASP.NET Core 2.2，并发现有关于通用主机的参考资料。

我尝试按照示例创建带有backgroundService的控制台应用程序：https://github.com/aspnet/AspNetCore.Docs/tree/master/aspnetcore/fundamentals/host/generic-host/samples/

var param = Console.ReadLine();

var host = new HostBuilder().ConfigureServices((hostContext, services) =>
{
   services.AddHostedService<MyCustomSerivce>();
}

问题在于如何从命令行中传递参数（在我的情况下是“param”），以指定特定后台服务中的内部逻辑。

- Kyre

在高层次上，您应该使用内置的配置系统并将命令行参数添加到配置中。然后，服务可以通过 DI 获取配置对象。 - juunas

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- Edward · Accepted Answer

为了解决服务问题，您需要将参数注册到服务集合中。

Service for storing the parameter

public class CommandLineArgs
{
    public string Args { get; set; }
}

Register the parameter

public class Program
{
    public static async Task Main(string[] args)
    {
        var param = Console.ReadLine();

        var host = new HostBuilder()
            .ConfigureHostConfiguration(configHost =>
            {
                configHost.SetBasePath(Directory.GetCurrentDirectory());
                configHost.AddJsonFile("hostsettings.json", optional: true);
                configHost.AddEnvironmentVariables(prefix: "PREFIX_");
                configHost.AddCommandLine(args);
            })
            .ConfigureAppConfiguration((hostContext, configApp) =>
            {
                configApp.AddJsonFile("appsettings.json", optional: true);
                configApp.AddJsonFile(
                    $"appsettings.{hostContext.HostingEnvironment.EnvironmentName}.json", 
                    optional: true);
                configApp.AddEnvironmentVariables(prefix: "PREFIX_");
                configApp.AddCommandLine(args);
            })
            .ConfigureServices((hostContext, services) =>
            {
                services.AddSingleton(new CommandLineArgs { Args = param });
                services.AddHostedService<LifetimeEventsHostedService>();
                services.AddHostedService<TimedHostedService>();
            })
            .ConfigureLogging((hostContext, configLogging) =>
            {
                configLogging.AddConsole();
                configLogging.AddDebug();
            })
            .UseConsoleLifetime()
            .Build();

        await host.RunAsync();
    }
}

Resolve service

internal class TimedHostedService : IHostedService, IDisposable
{
    private readonly ILogger _logger;
    private Timer _timer;
    private readonly IConfiguration _configuration;
    private readonly CommandLineArgs _commandLineArgs;
    public TimedHostedService(ILogger<TimedHostedService> logger
        , IConfiguration configuration
        , CommandLineArgs commandLineArgs)
    {
        _logger = logger;
        _configuration = configuration;
        _commandLineArgs = commandLineArgs;
    }       
}