[API Proposal]: Allow UseWindowsService and UseSystemd to indicate whether they've activated

[jez9999]

Background and motivation

The .UseWindowsService() and .UseSystemd() extensions allow a host builder to be configured to run as a Windows or systemd service if it's detected that they're currently running in one of those contexts, but it'd be useful for the program to actually know whether that activation happened. They should therefore be able to report back as to whether they detected that the current program was running as a Windows or systemd service, and therefore activated.

API Proposal

namespace Microsoft.Extensions.Hosting;

public static class WindowsServiceLifetimeHostBuilderExtensions
{
    public static (bool? WasActivated, IHostBuilder Builder) UseWindowsService(this IHostBuilder hostBuilder, Action<WindowsServiceLifetimeOptions> configure, bool indicateWhetherActivated = false)
}

namespace Microsoft.Extensions.Hosting;

public static class SystemdHostBuilderExtensions
{
    public static (bool? WasActivated, IHostBuilder Builder) UseSystemd(this IHostBuilder hostBuilder, bool indicateWhetherActivated = false)
}

API Usage

var builder = Host.CreateDefaultBuilder(args);
(var isWinService, _) = builder.UseWindowsService(x => x.ServiceName = "MyService", true);
(var isSystemdService, _) = builder.UseSystemd(true);

Alternative Designs

No response

Risks

No response

[ghost]

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Issue Details

---

### Background and motivation The `.UseWindowsService()` and `.UseSystemd()` extensions allow a host builder to be configured to run as a Windows or systemd service if it's detected that they're currently running in one of those contexts, but it'd be useful for the program to actually know whether that activation happened. They should therefore be able to report back as to whether they detected that the current program was running as a Windows or systemd service, and therefore activated. ### API Proposal ```csharp namespace Microsoft.Extensions.Hosting; public static class WindowsServiceLifetimeHostBuilderExtensions { public static (bool? WasActivated, IHostBuilder Builder) UseWindowsService(this IHostBuilder hostBuilder, Action configure, bool indicateWhetherActivated = false) } ``` ```csharp namespace Microsoft.Extensions.Hosting; public static class SystemdHostBuilderExtensions { public static (bool? WasActivated, IHostBuilder Builder) UseSystemd(this IHostBuilder hostBuilder, bool indicateWhetherActivated = false) } ``` ### API Usage ```csharp var builder = Host.CreateDefaultBuilder(args); var isWinService = builder.UseWindowsService(x => x.ServiceName = "MyService", true); var isSystemdService = builder.UseSystemd(true); ``` ### Alternative Designs _No response_ ### Risks _No response_

Author:	jez9999
Assignees:	-
Labels:	`api-suggestion`, `untriaged`, `area-Extensions-Hosting`
Milestone:	-

[gfoidl]

You could use something like

using Microsoft.Extensions.Hosting.Systemd;
using Microsoft.Extensions.Hosting.WindowsServices;

public static bool IsRunAsService { get; } = IsRunAsServiceCore();

private static bool IsRunAsServiceCore()
{
    return WindowsServiceHelpers.IsWindowsService()
        || SystemdHelpers       .IsSystemdService();
}

Does this fit your needs?