[!code-csharp[Main](../../tutorials/first-web-api/sample/TodoApi/Controllers/TodoController2.cs?name=snippet_todo1)]

The preceding code:

* Defines an empty controller class. In the next sections, methods are added to implement the API.
* The constructor uses [Dependency Injection](xref:fundamentals/dependency-injection) to inject the database context (`TodoContext `) into the controller. The database context is used in each of the [CRUD](https://wikipedia.org/wiki/Create,_read,_update_and_delete) methods in the controller.
* The constructor adds an item to the in-memory database if one doesn't exist.

## Getting to-do items

To get to-do items, add the following methods to the `TodoController` class.

[!code-csharp[Main](../../tutorials/first-web-api/sample/TodoApi/Controllers/TodoController.cs?name=snippet_GetAll)]

These methods implement the two GET methods:

* `GET /api/todo`
* `GET /api/todo/{id}`

Here is an example HTTP response for the `GetAll` method:

```
[
  {
    "id": 1,
    "name": "Item1",
    "isComplete": false
  }
]
   ```

Later in the tutorial I'll show how the HTTP response can be viewed with [Postman](https://www.getpostman.com/) or [curl](https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man1/curl.1.html).

### Routing and URL paths

The `[HttpGet]` attribute specifies an HTTP GET method. The URL path for each method is constructed as follows:

* Take the template string in the controller's `Route` attribute:

[!code-csharp[Main](../../tutorials/first-web-api/sample/TodoApi/Controllers/TodoController.cs?name=TodoController&highlight=3)]

* Replaces `[controller]` with the name of the controller, which is the controller class name minus the "Controller" suffix. For this sample, the controller class name is **Todo**Controller and the root name is "todo". ASP.NET Core [routing](xref:mvc/controllers/routing) isn't case sensitive.
* If the `[HttpGet]` attribute has a route template (such as `[HttpGet("/products")]`, append that to the path. This sample doesn't use a template. See [Attribute routing with Http[Verb] attributes](xref:mvc/controllers/routing#attribute-routing-with-httpverb-attributes) for more information.

In the `GetById` method:

[!code-csharp[Main](../../tutorials/first-web-api/sample/TodoApi/Controllers/TodoController.cs?name=snippet_GetByID&highlight=1-2)]

`"{id}"` is a placeholder variable for the ID of the `todo` item. When `GetById` is invoked, it assigns the value of "{id}" in the URL to the method's `id` parameter.

`Name = "GetTodo"` creates a named route. Named routes:

* Enable the app to create an HTTP link using the route name.
* Are explained later in the tutorial.

### Return values

The `GetAll` method returns an `IEnumerable`. MVC automatically serializes the object to [JSON](http://www.json.org/) and writes the JSON into the body of the response message. The response code for this method is 200, assuming there are no unhandled exceptions. (Unhandled exceptions are translated into 5xx errors.)

In contrast, the `GetById` method returns the more general `IActionResult` type, which represents a wide range of return types. `GetById` has two different return types:

* If no item matches the requested ID, the method returns a 404 error. Returning `NotFound` returns an HTTP 404 response.

* Otherwise, the method returns 200 with a JSON response body. Returning `ObjectResult` returns an HTTP 200 response.