Intro

// ===== The values =====
// - Strong static typing with great inference (var, records, nullable refs)
// - .NET runtime: cross-platform, performant, mature
// - First-class async/await
// - Massive enterprise ecosystem (Web APIs, MAUI, Unity)

// ===== Hello, world =====
Console.WriteLine("hello, world");

// Top-level statements remove Main boilerplate.
// dotnet new console; dotnet run

// ===== Records + pattern matching =====
public record User(int Id, string Name, string Email);

var u = new User(1, "Alex", "a@x.io");
var size = u.Id switch {
    < 10 => "small",
    < 100 => "medium",
    _ => "large",
};

// ===== Async by default =====
public async Task<string> FetchTitleAsync(string url)
{
    using var http = new HttpClient();
    return await http.GetStringAsync(url);
}

// ===== Minimal Web API (ASP.NET Core) =====
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet("/healthz", () => Results.Json(new { ok = true }));
app.Run();

// dotnet run -> http://localhost:5000/healthz

// ===== When C# wins =====
// - Enterprise systems
// - Game development (Unity)
// - Cross-platform desktop (.NET MAUI)
// - High-performance APIs (Kestrel + minimal APIs are very fast)

// ===== When C# hurts =====
// - Quick dynamic scripting (Python wins)
// - Anywhere you'd rather not depend on .NET runtime tooling

// ===== Patterns to internalise =====
// - Records for DTOs
// - Nullable reference types enabled in every project
// - async all the way down at IO boundaries
// - DI built into ASP.NET Core; don't roll your own

// ===== Pitfalls =====
// - Using .Result on a Task -> deadlocks in UI / ASP.NET
// - Disabling nullable warnings to silence errors -> hides real bugs
// - Catching general Exception broadly
// - Manually managing connections instead of using async + 'using'

// C#: statically typed, OOP, runs on .NET.
// Modern features: records, top-level statements, async/await, LINQ.