Section 1.1: The Evolution of API Development

Previously, even the most straightforward web services in ASP.NET Core required substantial boilerplate code when juxtaposed with other web development frameworks. For instance, a simple "Hello World" web service with a single endpoint returning plain text could be accomplished in merely nine lines of code using Express.js. In contrast, achieving the same outcome with ASP.NET Core 5 or earlier versions demanded over fifty lines of code.

With the introduction of ASP.NET Core 6 and the advent of Minimal APIs, this has drastically changed. Now, it takes just five lines of code and an additional six lines for configuration to achieve the same functionality, as illustrated in the upcoming code snippets.

Section 1.2: Simplifying Route Mappings

Route mappings in Minimal APIs are straightforward:

• MapGet: Assigns a route for GET requests to fetch an entity.
• MapPost: Allocates a route for POST requests to insert an entity.
• MapPut: Designates a route for PUT requests to modify an entity.
• MapPatch: Sets a route for PATCH requests to update an entity.
• MapDelete: Binds a route for DELETE requests to remove an entity.
• MapMethods: Allows routing for other HTTP methods, such as CONNECT or HEAD.

Parameter mapping can also be easily managed using attributes to indicate how parameters should be populated:

• [FromServices]: Sets the parameter from registered dependency services.
• [FromRoute]: Fetches the parameter from a corresponding named route segment.
• [FromQuery]: Utilizes a matching named query string parameter.
• [FromBody]: Sources the parameter from the HTTP request body.

Example Code Snippet:

public static WebApplication MapGets(this WebApplication app, int pageSize = 10)

{

app.MapGet("/", () => "Hello World!")

.ExcludeFromDescription();

app.MapGet("api/todos", ([FromServices] TodoContext db, [FromQuery] int? page) =>

{

return db.Todos

.OrderBy(todo => todo.Id)

.Skip(((page ?? 1) - 1) * pageSize)

.Take(pageSize);

})

.WithName("GetTodos")

.Produces();

return app;

}

Section 1.3: Documenting Your APIs

It's essential to clearly define the expected return types and status codes for your endpoints. You can utilize methods like Produces<T>(StatusCodes.Status200OK) to specify that a successful response will return a type T along with a status code of 200. Similarly, Produces(StatusCodes.Status404NotFound) indicates that if no matching route is found, the response will be empty with a 404 status code.