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273 lines
9.2 KiB
Markdown
273 lines
9.2 KiB
Markdown
---
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marp: true
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paginate: true
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math: mathjax
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theme: buutti
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title: 4. RESTful HTTP Methods
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---
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# RESTful HTTP Methods
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<!-- headingDivider: 5 -->
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<!-- class: invert -->
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## Contents
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- [HTTP methods for RESTful APIs](#http-methods-for-restful-apis)
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- [HTTP `POST` method](#http-post-method)
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- [HTTP `PUT` method](#http-put-method)
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- [HTTP `DELETE` method](#http-delete-method)
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- [HTTP `PATCH` method](#http-patch-method)
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## HTTP methods for RESTful APIs
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### RESTful API
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* We'll be extending our Web API into a full-blown ***RESTful API***
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* More about REST in [Frontend Basics Lecture 3: REST Architecture](https://gitea.buutti.com/education/frontend-basics/src/branch/main/3-rest-architecture.md)
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* A good idea to also check out [Frontend Basics Lecture 2: HTTP methods](https://gitea.buutti.com/education/frontend-basics/src/branch/main/2-http.md)
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* We have so far implemented `GET` and `POST` methods for reading resources from the API and creating new ones to it, respectively
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* All the primary methods for following the uniform interface requirement are `GET`, `POST`, `PUT`, `PATCH` and `DELETE`
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* Others exist, but these are by far most commonly used
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* These methods correspond to ***CRUD*** operations *__Create__*, *__Read__*, *__Update__* and *__Delete__*
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* CRUD describes what is done to a resource after a request is sent
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### Primary HTTP request methods
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The primary HTTP request methods with descriptions:
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| Method | Attribute | Description |
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|:--------|:---------------|:------------------------------------------|
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| `GET` | `[HttpGet]` | ***Read*** a representation of a resource |
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| `POST` | `[HttpPost]` | ***Create*** new resources |
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| `PUT` | `[HttpPut]` | Fully ***update*** an existing resource |
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| `PATCH` | `[HttpPatch]` | Partially ***update*** an existing resource |
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| `DELETE` | `[HttpDelete]` | ***Delete*** a resource |
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[https://www.restapitutorial.com/lessons/httpmethods.html](https://www.restapitutorial.com/lessons/httpmethods.html)
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## HTTP `POST` method
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### Handling `HttpPost` Requests
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* Remember that HTTP requests can include a content body
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* In ASP.NET, this content is assigned to a variable with the `[FromBody]` attribute:
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```csharp
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[HttpPost]
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public string[] Post([FromBody] string someContent)
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{
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// someContent holds the content of the request body
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return new string[] { text };
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}
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```
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* Note that the `[FromBody]` attribute can only be used on one parameter
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* However, nothing prevents you from using a custom type variable
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---
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* ASP.NET deserializes the request content body into an object:
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```csharp
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// Models/Contact.cs
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public class Contact
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{
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public int Id { get; set; }
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public string Name { get; set; }
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}
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```
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* ```csharp
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// Controllers/ContactsController.cs
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[HttpPost]
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public Contact Put(int id, [FromBody] Contact contact)
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{
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// Contacts is a list of Contact objects, fetched from some repository
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Contacts.Add(contact);
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return contact;
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}
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```
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### Creating a POST Request with Postman
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#### Request headers
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* ASP.NET knows to deserialize the content if the content type is set to JSON in the HTTP requests *__headers__*
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* Headers are optional parameters that can be included in every HTTP request
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* Headers are set in a Key-Value format
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* When creating a request in Postman, to inform the server what type of content was just sent, add a new key `Content-Type` and set its value to `application/json` in the _Headers_ tab:
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<div class='centered'>
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</div>
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#### Request body
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After setting the header,
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1) select the Body tab,
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2) change the content type to raw,
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3) select JSON from the dropdown menu, and
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4) insert the content in JSON format
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<div class='centered'>
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</div>
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#### Sending the request
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* If the `POST` method is routed at `http://localhost:54106/api/contacts`:
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<div class='centered'>
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</div>
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### Exercise 1: Creating a `POST` Endpoint
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<!--_class: "exercise invert" -->
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Continue working on the CourseAPI.
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1) Create a `POST` method and endpoint which adds a new course to the list in the repository with a running ID. Content and Author values are obtained from the request body:
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## HTTP `PUT` method
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* Use `PUT` to replace an existing resource, e.g. an element in a list, with a new one
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* The ID of the resource to be replaced should be in the request URI
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* The information about the new resource should be in the request body like in `POST` requests
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<div class='centered'>
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</div>
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### Handling `HttpPut` requests
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* The ID is fetched from the URI and the contents from the request body
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* Filtering is used to copy all objects from the original list except for the new `contact` object, which comes from body
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```csharp
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// Controllers/ContactsController.cs
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[HttpPut("{id}")]
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public List<Contact> Put(int id, [FromBody] Contact contact)
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{
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// Contacts is a list of Contact objects, fetched from some repository
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List<Contact> updatedList = Contacts.Select(c => c.Id != id ? c : contact).ToList();
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Contacts = updatedList;
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return updatedList;
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}
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```
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### Exercise 2: Creating a `PUT` Endpoint
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* In CoursesController class, create a method for PUT requests with the URI api/courses/{id}
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* The ID of the course to be replaced with should be in the request URI and the contents of the new course should be in the request body.
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* The method should replace the corresponding course from the Courses list in the repository with the new course.
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* The method should return the updated Courses list (for testing purposes)
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* Return a 404 status code if a course with the corresponding ID does not exist
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* Test with Swagger/Postman
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## HTTP `DELETE` method
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* Use `DELETE` to delete an existing resource, e.g. an element in a list
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* The ID of the resource to be deleted should be in the request URI
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* As with the `GET` method, a body is not needed
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### Handling `HttpDelete` Requests
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* The ID is fetched from the URI
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```csharp
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// Controllers/ContactsController.cs
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[HttpDelete("{id}")]
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public List<Contact> Delete(int id)
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{
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// Contacts = list of contact objects, fetched from some repository
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List<Contact> updatedList = Contacts.Where(c => c.Id != id).ToList();
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Contacts = updatedList;
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return Contacts;
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}
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```
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### Exercise 3: Creating a `DELETE` Endpoint
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<!--_class: "exercise invert" -->
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Continue working on CourseAPI.
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1) Create an endpoint for `DELETE` requests with the URI `api/courses/{id}`
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a) The ID of the course should be fetched from the URI
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b) The corresponding course should be removed from the list of courses in the repository
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c) The method should return the updated `Courses` list (for testing purposes)
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d) Return a `404` status code if a course with the corresponding ID does not exist
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2) Test with Postman.
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## HTTP `PATCH` method
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* Use `PATCH` to *partially* update a resource
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* I.e., update some value inside of a resource
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* This saves some resources as only a part of a resource has to be sent instead of an entire document (as opposed to `PUT` requests)
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* Sending and handling `PATCH` requests with ASP.NET requires some extra work and the use of a third party package [JSON Patch](http://jsonpatch.com/)
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---
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* To handle `PATCH` requests in a standardized way, install and add the following NuGet packages to your project:
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* `Microsoft.AspNetCore.JsonPatch`
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* `Microsoft.AspNetCore.Mvc.NewtonsoftJson`
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* Then, change the following line in `Program.cs`:
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```csharp
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builder.Services.AddControllers();
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```
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* to this:
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```csharp
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builder.Services.AddControllers().AddNewtonsoftJson();
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```
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---
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* The body of the `PATCH` request needs to be in the following form:
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```json
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[{ "op": "replace", "path": "/propertyName", "value": "newValue"}]
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```
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* Use the URI to specify the ID of the resource to update
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<div class='centered'>
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</div>
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### Handling `HttpPatch` Requests
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* The ID is fetched from the URI
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* The property and its new value are specified in the body, which is retrieved as a `JsonPatchDocument`
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* `PATCH` is operated on the targeted object:
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```csharp
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// Controllers/ContactsController.cs
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[HttpPatch("{id}")]
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public List<Contact> Patch(int id, [FromBody] JsonPatchDocument<Contact> patchDocument)
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{
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// Contacts is a list of contact objects, fetched from some repository
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var contact = Contacts.FirstOrDefault(c => c.Id == id);
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if(contact != null)
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{
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patchDocument.ApplyTo(contact);
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}
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return Contacts;
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}
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```
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### Exercise 4: Creating a `PATCH` Endpoint
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<!--_class: "exercise invert" -->
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Continue working on CourseAPI.
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1) Create an endpoint for PATCH requests with the URI `api/courses/{id}`
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a) The ID of the course should be fetched from the URI
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b) The corresponding course should be updated according to the JSON PATCH document in the request body
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c) The method should return the updated `Courses` list (again, for testing purposes)
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d) Return a `404` status code if a course with the corresponding ID does not exist
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2) Test with Swagger/Postman. Try to change the number of credits for some course!
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