How to use appsettings.json in program.cs without warning "ASP0000 Calling 'BuildServiceProvider' from application code results in an copy ..."

Question

I am building a .net minimal api with a lot of settings defined via appsettings.json.

But how to use this setting classes in program.cs without the compiler generating the warning:

ASP0000 Calling 'BuildServiceProvider' from application code results in an additional copy of singleton services being created. Consider alternatives such as dependency injecting services as parameters to 'Configure'.

What I do is:

var builder = WebApplication.CreateBuilder(args); // Create a WebApplication builder
builder.Services.AddEndpointsApiExplorer();

builder.Services.Configure<MYSettingFromAppsettings>(
    builder.Configuration.GetSection(MYSettingFromAppsettings.Position));
builder.Services.AddSingleton(resolver =>
    resolver.GetRequiredService<IOptions<MYSettingFromAppsettings>>().Value);

...//same for all the other settings

var corsConfig = builder.Services.BuildServiceProvider().GetRequiredService<MYSettingFromAppsettings>();

// use settings

To be clear, I do not only use the settings in program.cs I also us it via DI in the services (IOptions options)

So, what is best practice to work with type save setting classes in program.cs and also via DI?

Answer 1

The following:

var corsConfig = builder.Services.BuildServiceProvider().GetRequiredService<MYSettingFromAppsettings>();

Builds the service provider which should be avoided.

If you need to bind cofiguration before building container you can do something like:

var cfg = config.GetSection(MYSettingFromAppsettings.Position)
   .Get<MYSettingFromAppsettings>();

You can use the bound value (cfg) to register it in the DI container (though note that it will not reflect the configuration changes even if the provider supports it)