In .NET Core 3.0, we introduce a new type of application template called Worker Service. This template is designed to give you a starting point for writing long-running services in .NET Core. In this walkthrough, we will create a worker and run it as a Windows service.

Creation worker

Note. In our pre-release versions, the worker template is on the same menu as the web templates. This will change in a future release. We intend to place the Worker Service template directly in the Create New Project Wizard.

Creating a Worker in Visual Studio

Creating a Worker on the Command Line

Run dotnet new worker

Running as a Windows service

To start as a Windows service, we need our worker to see start and stop signals from the ServiceBase.NET type  , which connects Windows Service systems to .NET applications. To do this, you need:

Add NuGet Package Microsoft.Extensions.Hosting.WindowsServices

Add call  UseServiceBaseLifetime to  HostBuilder in Program.cs

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }
    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .UseServiceBaseLifetime()
            .ConfigureServices(services =>
            {
                services.AddHostedService();
            });
}

This method does a few things. Firstly, it checks if the application really works as a Windows service, if it is not, then it performs noops, which makes this method safe to call when running locally or as a Windows service.

Secondly, it configures your host to use  ServiceBaseLifetime. ServiceBaseLifetime works with  ServiceBase to help control the lifetime of your application when it starts as a Windows service. This overrides the standard one  ConsoleLifetime that processes signals such as CTL + C.

Install Worker

Once we got the worker using ServiceBaseLifetime we need to install it:

First, let's publish the app. We will install the Windows Service in-place, which means that the executable will be blocked every time the service starts. Publishing is a good way to make sure that all the files needed to start the service are in one place and ready to install.

dotnet publish -o c:\code\workerpub

Next, you can use  sc utility  in the admin command line

sc create workertest binPath=c:\code\workerpub\WorkerTest.exe

For instance:

Security note:  This command starts the service as a local system, which is  not what you need . Instead, you should create a service account and start the Windows service as this account. We will not talk about this here, but there is some ASP.NET documentation here:  https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/windows-service?view=aspnetcore- 2.2

Logging

The logging system has an Event Log service, which can send log messages directly to the Windows event log. To enter the event log, you can add a  Microsoft.Extensions.Logging.EventLog package and then change yours  Program.cs:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureLogging(loggerFactory => loggerFactory.AddEventLog())
        .ConfigureServices(services =>
        {
            services.AddHostedService();
        });

Further work

In the following previews, we plan to improve the use of Workers with Windows Services:

1. Rename UseWindowsServiceBaseLifetime to UseWindowsService
2. Add automatic and improved integration with the event log at startup as a Windows service.

Conclusion

We hope that you will try out our new template and want to know how it works. You can send any error messages or suggestions here:  https://github.com/aspnet/AspNetCore/issues/new/choose

Glenn condron