Allows specifying default configuration values in code while still allowing other sources to override

DefaultConfigProvider.cs

using Microsoft.Extensions.Configuration.Memory;

var builder = WebApplication.CreateBuilder(args);

builder.Configuration.AddConfigurationDefaults(new()
{
    { "request:timeout", "60" }
});

var app = builder.Build();

// Show example of manually binding from configuration
var config = new Config();
app.Configuration.GetSection("request").Bind(config);

app.MapGet("/", () => config.Timeout);

app.Run();

class Config
{
    public int Timeout { get; set; }
}

public static class ConfigurationExtensions
{
    public static IConfigurationBuilder AddConfigurationDefaults(this IConfigurationBuilder configurationBuilder, Dictionary<string, string?> defaults)
    {
        // Insert at 0 so that other configuraton sources can override the defaults
        configurationBuilder.Sources.Insert(0, new MemoryConfigurationSource()
        {
            InitialData = defaults
        });

        return configurationBuilder;
    }
}