[API Proposal]: Like WebApplicationBuilder allow us to put a finished IConfiugration instance into a HostBuilder

[drauch]

For internal reasons we create and validate the IConfiguration instance before building hosts. The .NET 6 WebApplicationBuilder lets us register this instance directly at the container:

var builder = WebApplicationBuilder.CreateBuilder();
OurConfigurationUtility.SetUp(builder.Configuration);

builder.Services.AddSingleton<IConfiguration>(builder.Configuration);
 
var startup = new Startup(builder.Configuration);
startup.ConfigureServices(builder.Services);
 
var app = builder.Build();
 
startup.Configure(app, app.Environment);
 
app.Run();

However, for our non-web background services we can't do the same with HostBuilder. To our knowledge there is only the ConfigureAppConfiguration method which already puts in some defaults and lets you work with a ConfigurationBuilder but there is no way to put a finished IConfiguration instance in, is there?

Best regards,
D.R.

[julealgon]

You should still be able to register your own singleton instance the exact same way using ConfigureServices:

.ConfigureServices((context, services) =>
{
    OurConfigurationUtility.SetUp(context.Configuration);
    
    services.AddSingleton<IConfiguration>(context.Configuration);
})

I'm just confused by your usage there... you pass in the configuration, and then your method does mutations to it? Regardless... I believe the above should still work, although I'm not sure whether that registration will be overridden by the Host.Build() call later.

Why do you have this external configuration method in the first place?

[tarekgh]

Can't you do something like:

hostBuilder.ConfigureAppConfiguration((context, config) =>
{
    config.Sources.Clear(); // Clear existing configuration sources
    // then add your configuration the config
});

[drauch]

@julealgon : Unfortunately, it looks like the registration of the HostBuilder takes precedences as it is registered later on.
@tarekgh : I already have an IConfiguration instance, so clearing the sources does not do anything. Except there is a way to put an IConfiguration back in as a configuration source ... but that sounds like a hack at best.

Best regards,
D.R.

[julealgon]

I already have an IConfiguration instance, so clearing the sources does not do anything. Except there is a way to put an IConfiguration back in as a configuration source ... but that sounds like a hack at best.

@drauch you could technically add an inmemory configuration provider and pass your settings from your previously built IConfiguration.

hostBuilder.ConfigureAppConfiguration((context, config) =>
{
    config.Sources.Clear();
    config.AddInMemoryCollection(yourPreBuiltConfiguration.AsEnumerable());
});

I'm not sure how efficient this is, but it should work at least as a temporary workaround for you.