Drill 3: Real project — A minimal ASP.NET API

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

app.MapGet("/api/courses", async (AppDb db) =>
    Results.Ok(await db.Courses.ToListAsync()));

app.MapPost("/api/courses", async (CourseInput input, AppDb db) =>
{
    if (string.IsNullOrWhiteSpace(input.Title))
        return Results.BadRequest(new { error = "INVALID_TITLE" });

    var course = new Course(Guid.NewGuid(), input.Title, input.Lessons);
    db.Courses.Add(course);
    await db.SaveChangesAsync();
    return Results.Created("/api/courses/" + course.Id, course);
});

app.Run();