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Our EntriesController action methods are
currently using IEnumerable of type Entry,

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entry are void for their return types.

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When returning a type like
IEnumerable of type Entry, or entry,

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Web API will serialize the return
value to the response message body,

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and set the response's
HTTP StatusCode to 200 OK.

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When returning void,
Web API will simply return a response with

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an HTTP StatusCode of 204 No Content.

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When we were designing our API in
the first section of this course,

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we discussed that we wanted our API to
return appropriate responses with commonly

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used HTTP status codes.

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For example, in our second get action
method if a resource isn't found for

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the provided ID parameter value, we should
we turn a 404 Not Found StatusCode.

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And in the Post action method instead of
returning a 204 No Content StatusCode,

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we should return 201 Created,

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indicating that the request led
to the creation of a resource.

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Web API provides a set of built-in HTTP

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action result types that we can
use to refine our responses.

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To make these types even easier to
use the API controller base class,

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provides a set of helper methods
that we can call that'll return

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one one of the HTTP action result types.

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For example,
to return an OK negotiated content result,

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HTTP action result type,
we can call the OK method.

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Passing in the content to
write to the message body.

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Calling the OK method will return
a response with a 200 OK HTTP StatusCode.

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Now that we're returning
an HTTP action result type,

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we need to change our return type to
the IHhttpActionResult interface.

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Under the covers, HTTPActionResult
types handle the creation and

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configuration of an HTTP response message.

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And if you encounter a scenario that one
of the built in HTTPActionResult types

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doesn't cover, you can create your
own custom HTTPActionResult type.

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For a complete list of the API
controllers, HTTPActionResult helper

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methods, or for more information
on the HTTP response message type.

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Or how to create your own
custom HTTPActionResult types,

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see the teacher's notes.

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Now, let's update our remaining control or
action methods.

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In the second GET action method, let's
handle the case when a resource isn't

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found for the provided ID parameter value.

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Let's start by changing the methods
return typed IHttpActionResult.

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Then, let's capture our call to
the entriesRepository.Get method into

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a variable named entry.

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Then we can check if
the entry variable is null.

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And if it is null, we can return
a call to the NotFound method.

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That'll return a response with
a 404 NotFound HTTP StatusCode,

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then at the bottom of the method
return a call to the Ok method.

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Passing then our entry variable.

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Moving on to the POST method start
by changing the return type from

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void to IHttpActionResult.

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Then, simply return a call
the to the Created method.

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The Created method will return or response
with the 201 Created HTTP StatusCode.

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The Created method accepts two parameter
values, a URI representing the location

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for the newly created resource, and
the object for the resource itself.

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We can generate the URI by making
a call to the Url.Link method.

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The first parameter that we pass
to the link method is the name of

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the route template to use,
which in our case is DefaultAPI.

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That's the name for
the route template for our default route.

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For the second parameter,
we need to pass an anonymous object for

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the route parameter values.

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Controller = the name of our controller.

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And id = entry.Id.

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For the created method second parameter,
we need to pass in our entry object.

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The Put and Delete action methods
are okay as they are, at least for now.

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We'll update the Put method along
with the POST method again,

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later in this section when we handle
implementing our validations.

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Leave in the delete method with the void
return type will result in a response

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with an empty message body and
an HTTP StatusCode of 204 No Content.

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Which happens to be
an appropriate response for

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successfully deleting a resource.

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Let's test the changes to
our entries controller.

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In Postman let's request a single
resource from the entries endpoint.

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The path will be API/entries/1,
and click the Send button.

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Down here on the bottom,

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we can see the JSON formatted data
that was sent in the message body.

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And we can see that the responses
HTTP StatusCode was 200 OK.

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Now let's request a single
resource that we know won't exist,

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by providing an ID wrap-router
value of let's say 999.

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Now we can see that
the message body was empty, and

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the responses HTTP status
code was 400 Not Found.

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Now let's try creating a new resource.

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Select POST in the list of HTTP methods,
and

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provide the URI path, API/entries.

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Click on the Body tab, select raw, and for

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the content media type,
select JSON(application/json).

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To save time I have the JSON formatted
data for our message body here in Notepad.

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If you're following along, see the
teacher's notes for a copy of this data.

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Click in the message body field,
and paste from the clip board,

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then click the Send button.

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Scroll down to the see the response,
and here's the message body containing

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the data for
the new resource that was created.

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And we can see here that the Status was
201 Created Clicking on the Headers tab,

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allows us to see that the Location Header
is set to the URI for the new resource.