How to use IOptions pattern in Program.cs in .NET6, before builder.build()?

Question

Using the options pattern in .NET6, I can get access to some config values as follows:

builder.Services.Configure<ApiConfiguration>(
    builder.Configuration.GetSection(ApiConfiguration.Api));

var app = builder.Build();

var options = app.Services.GetRequiredService<IOptions<ApiConfiguration>>().Value;

However, I would like to get the Options before builder.Build(), so I can use the appSettings values when adding some Services to the ServiceCollections.

I haven't been able to find it anywhere yet, so I am wondering if it is even possible (and how ofcourse :D )

Answer 1

In the default DI container services can't be resolved before it is built and building the container multiple times is not a recommended approach (for multiple reasons). If you need settings before the application is built you can access them without the options pattern:

var settings = builder.Configuration
    .GetSection(ApiConfiguration.Api)
    .Get<ApiConfiguration>();

Answer 2

so I can use the appSettings values when adding some Services to the ServiceCollections.

This sounds wrong to me as IOptions are part of DI container and can be injected in the constructor.

builder.Services.AddScoped<Service>();

...

public class Service
{
    private readonly ApiConfiguration myOptions;
    
    public Service(IOptions<ApiConfiguration> options)
    {
        myOptions = options.Value;
    }
}

If your class can't rely on IOptions like in the example below

public class Service
{
    private readonly ApiConfiguration myOptions;
    
    public Service(ApiConfiguration options)
    {
        myOptions = options;
    }
}

, use a factory method instead:

builder.Services.AddScoped<ApiConfiguration>(sp => sp.GetRequiredService<IOptions<ApiConfiguration>>().Value);
builder.Services.AddScoped<Service>();

OR

builder.Services.AddScoped<Service>(sp => new Service(sp.GetRequiredService<IOptions<ApiConfiguration>>().Value));