What are minimal APIs in ASP.NET Core?

Question

Accepted Answer

**Minimal APIs** — lightweight API development without controllers.

**Basic:**
```csharp
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapGet("/", () => "Hello World!");
app.MapGet("/users/{id}", (int id) => $"User {id}");
app.Run();
```

**With parameters:**
```csharp
app.MapGet("/users/{id}", async (int id, IUserService service) =>
{
    var user = await service.GetByIdAsync(id);
    return user is not null
        ? Results.Ok(user)
        : Results.NotFound();
});
```

**POST with body:**
```csharp
app.MapPost("/users", async (CreateUserDto dto, IUserService service) =>
{
    var user = await service.CreateAsync(dto);
    return Results.Created($"/users/{user.Id}", user);
});
```

**Route groups:**
```csharp
var api = app.MapGroup("/api");
var users = api.MapGroup("/users");

users.MapGet("/", GetAllUsers);
users.MapGet("/{id}", GetUserById);
users.MapPost("/", CreateUser);
```

**Benefits:**
- Less boilerplate.
- Faster startup.
- AOT compatible.
- Great for microservices.

C#: What are minimal APIs in ASP.NET Core?