Expose a JSON dataset as an HTTP API with minimal C# code

JsonApi.cs

using System.Text.Json;

var jsonDocument = JsonSerializer.Deserialize<JsonElement>("""
{
    "Germany": { "Population":  83783942, "Language":  "German" },
    "France": { "Population":  65273511, "Language":  "French" },
    "the Netherlands": { "Population":  17134872, "Language":  "Dutch" }
}
""");

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

// Return full jsonDocument for the root URI
app.MapGet("/", () => Results.Json(jsonDocument));

// Return a single object or string for URIs like /Germany or /France/Language
// or a 404 if the specified path does not exist
app.MapGet("/{*path}", (string path) =>
{
    try
    {
        var result = path.Split("/").Aggregate(
            jsonDocument,
            (jsonElement, pathSegment) => jsonElement.GetProperty(pathSegment));

        return Results.Json(result);
    }
    catch (Exception ex) when (ex is KeyNotFoundException or InvalidOperationException)
    {
        return Results.NotFound();
    }
});

app.Run();

$ curl -i "http://localhost:5107/France/Language"
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8

"French"

$ curl -i "http://localhost:5107/Germany"
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8

{"Population":83783942,"Language":"German"}

$ curl -i "http://localhost:5107/Mexico"
HTTP/1.1 404 Not Found