CreateDefaultBuilder & ConfigureWebHost/ConfigureWebHostDefaults are broken

[Kaelum]

Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});

The above code is being using in multiple places, but it fails if the StartUp class constructor contains something like "ILogger<Startup> logger" in addition to the "IConfiguration configuration". If you don't use the "Host.CreateDefaultBuilder()", and instead start with a WebHostBuilder object, everything works as expected. I am using the following constructor:

public Startup(ILogger<Startup> logger, IConfiguration configuration)
{
Logger = logger;
Configuration = configuration;
}

Which works perfectly when starting with a WebHostBuilder object, but fails with the following exception when starting with the HostBuilder objects:

System.InvalidOperationException: Unable to resolve service for type 'Microsoft.Extensions.Logging.ILogger`1[Webroot.Bcap.WebApi.Startup]' while attempting to activate 'Webroot.Bcap.WebApi.Startup'.

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Document Details

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• ID: c3460b0d-9c60-3a06-ac63-18cf990e53c3
• Version Independent ID: b2dece1f-15b8-03af-6d52-7cc070432b4b
• Content: Background tasks with hosted services in ASP.NET Core
• Content Source: aspnetcore/fundamentals/host/hosted-services.md
• Product: aspnet-core
• Technology: aspnetcore-fundamentals
• GitHub Login: @guardrex
• Microsoft Alias: riande

[guardrex]

That's correct. That's the new 3.0 behavior. See 👉 aspnet/Announcements#353.

Inject your logger directly into Startup.Configure ...

https://docs.microsoft.com/aspnet/core/fundamentals/logging/#create-logs-in-the-startup-class

If you need it in Startup.ConfigureServices, call GetRequiredService for an instance ...

var logger = services.GetRequiredService<ILogger<Program>>();

[Kaelum]

For those who see this after the issue was closed, here is a link to the thread where they try to defend this change, but fail miserably:

[Announcement] Generic Host restricts Startup constructor injection

If you are using NLog, you can use the following line as a work-around for this ridiculous issue:

		Logger = LogManager.GetCurrentClassLogger();