How to pass parameters for BackgroundService?

Question

I read about ASP.net core 2.2 and I found reference about generic host.

I tried to create console app with backgroundService under example: 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>();
}

The problem is how can be passed argument from command line (in my case 'param'), that will specified internal logic in particular background service.

At a high level, you should use the built-in configuration system and add the command line params to the config. The service can then get configuration objects through DI. — juunas

Edward Edward · Accepted Answer · 2019-06-27T07:06:26

For resolving service, you need to register the parameters into service collection.

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;
    }       
}

How to pass parameters for BackgroundService?

1 Answers