Excellent rest using asp.net web api

Excellent REST using ASP.NET WebApi

Maurice de Beijer

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Who am I?

• Maurice de Beijer• The Problem Solver• Microsoft Integration MVP• DevelopMentor instructor• Twitter:@mauricedb• Blog: http://msmvps.com/blogs/theproblemsolver/ • Web: http://www.HTML5Support.nl • E-mail: [email protected]

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What are we going to cover?

• What is REST?• What is ASP.NET WebAPI• Hypermedia

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What is REST?

Representational State Transfer (REST) is an architectural style that abstracts

the architectural elements within a distributed hypermedia system.

Wikipedia

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What is REST?

• First conceived by Roy Thomas Fielding– Part of his doctoral thesis from 2000– One of the original authors of the Hypertext Transfer Protocol

-- HTTP/1.0• A way of creating “web services”

– Based on the HTTP standard

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Hypertext Transfer Protocol

The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed,

collaborative, hypermedia information systems. It is a generic, stateless, protocol which can be

used for many tasks beyond its use for hypertext.

The Internet Engineering Task Force

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Richardson Maturity Model

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ASP.NET WebAPI

ASP.NET Web API is a framework that makes it easy to build HTTP and REST services using

the .NET framework.

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WebAPI Controllers

• An ApiController does the work– Access to the HTTP Request and Response

• Use ModelBinding to ease working with resources– But also provides HttpRequestMessage for low level access

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WebAPI Controllers

• Lots of control about sending resources to the client– HttpResponseMessage– Content negotiation

• Set any HTTP header you like– Caching– Optimistic concurrency

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WebAPI Controllers

public class DemoController : ApiController{ // GET api/demo public IEnumerable<string> Get() { return new string[] { "value1", "value2" }; }}

public class DemoController : ApiController{ // GET api/demo public IEnumerable<string> Get() { return new string[] { "value1", "value2" }; }}

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WebAPI Routes

• Couple an incoming URL to an ApiController– Just like with ASP.NET MVC

• Create as many as you like– The ordering is important!

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WebAPI Routes

public static void Register(HttpConfiguration config){ config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } );}

public static void Register(HttpConfiguration config){ config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } );}

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Content negotiation

• What resource we send != how we send it– JSON of XML: a book resource is still a book resource

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MediaTypeFormatter

• The media type specifies the serialization format– JSON, XML, Word, PDF, VCard etc

• The MediaTypeFormatter (de)serializes– HTTP <> CLR type

• Content negotiation determines the serialized format– The client uses the HTTP Accept header

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MediaTypeFormatter

public class CustomersTextFormatter : BufferedMediaTypeFormatter{ public CustomersTextFormatter() { SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/text")); }

public override bool CanWriteType(Type type) { return typeof(IEnumerable<Customer>).IsAssignableFrom(type); }

public override void WriteToStream(Type type, object value, Stream writeStream, HttpContent content)

{ // ... }}

public class CustomersTextFormatter : BufferedMediaTypeFormatter{ public CustomersTextFormatter() { SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/text")); }

public override bool CanWriteType(Type type) { return typeof(IEnumerable<Customer>).IsAssignableFrom(type); }

public override void WriteToStream(Type type, object value, Stream writeStream, HttpContent content)

{ // ... }}

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HTTP Methods

• HTTP supports many HTTP Methods– With HTML we only use two

• The HTTP Method determines our goal– Just like the database CRUD actions

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HTTP Methods

Aktie HTTP Method

Create POST

Read GET

Update (completly replace) PUT

Update (partial replace) PATCH

Delete DELETE

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WebAPI HTTP Methods

public class DemoController : ApiController { // GET api/demo public IEnumerable<string> Get()

// GET api/demo/5 public string Get(int id)

// POST api/demo public void Post([FromBody]string value)

// PUT api/demo/5 public void Put(int id, [FromBody]string value)

// DELETE api/demo/5 public void Delete(int id)}

public class DemoController : ApiController { // GET api/demo public IEnumerable<string> Get()

// GET api/demo/5 public string Get(int id)

// POST api/demo public void Post([FromBody]string value)

// PUT api/demo/5 public void Put(int id, [FromBody]string value)

// DELETE api/demo/5 public void Delete(int id)}

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Hypermedia - Roy T. Fielding

Hypermedia is defined by the presence of application control information embedded within, or

as a layer above, the presentation of information. Distributed hypermedia allows the presentation and

control information to be stored at remote locations.

Roy T. Fielding

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Richardson Maturity Model

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The OData Protocol

• Open Data Protocol (OData)– A hypermedia web protocol for retrieving and updating data.– Based on the W3C AtomPub standard

• Can include metadata• WCF Data Services is an implementation

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OData metadata

• An OData service can return metadata– http://www.nerddinner.com/Services/OData.svc/$metadata

• Enables generic clients like PowerPivot for Excel

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ASP.NET WebAPI and OData

• Standard ApiController’s support basic querying– $filter– $orderby– $skip– $take– $expand and $select support coming soon

• Needs to be explicitly enabled

public static void Register(HttpConfiguration config){ // Other config

config.EnableQuerySupport();}


config.EnableQuerySupport();}

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OData queries

public class CustomerController : ApiController{ private NorthwindEntities db =

new NorthwindEntities();

// GET api/Default2 [Queryable(PageSize=10)] public IQueryable<Customers> GetCustomers() { return db.Customers; }}

public class CustomerController : ApiController{ private NorthwindEntities db =

new NorthwindEntities();

// GET api/Default2 [Queryable(PageSize=10)] public IQueryable<Customers> GetCustomers() { return db.Customers; }}

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OData hypermedia controller

• The EntitySetController class can be used for more complete hypermedia support

• Build in support for Entity Framework Code First– But we can use any type we want

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OData metadata support

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OData hypermedia controller

public class HypermediaBooksController : EntitySetController<Book, int>{ private readonly IBooksRepository _repo = new BooksRepository();

// GET odata/hypermediaBooks public override IQueryable<Book> Get() { return _repo.GetBooks().AsQueryable(); }

// GET odata/hypermediaBooks(3) protected override Book GetEntityByKey(int key) { return _repo.GetBook(key); }}

public class HypermediaBooksController : EntitySetController<Book, int>{ private readonly IBooksRepository _repo = new BooksRepository();

// GET odata/hypermediaBooks public override IQueryable<Book> Get() { return _repo.GetBooks().AsQueryable(); }

// GET odata/hypermediaBooks(3) protected override Book GetEntityByKey(int key) { return _repo.GetBook(key); }}

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OData hypermedia routing


ODataModelBuilder modelBuilder = new ODataConventionModelBuilder(); modelBuilder.EntitySet<Book>("hypermediaBooks");

Microsoft.Data.Edm.IEdmModel model = modelBuilder.GetEdmModel(); config.Routes.MapODataRoute("ODataRoute", "odata", model);}


ODataModelBuilder modelBuilder = new ODataConventionModelBuilder(); modelBuilder.EntitySet<Book>("hypermediaBooks");

Microsoft.Data.Edm.IEdmModel model = modelBuilder.GetEdmModel(); config.Routes.MapODataRoute("ODataRoute", "odata", model);}

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Recommended reading

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Conclusion

• ASP.NET WebAPI makes REST “easy”– Even though sometimes ASP.NET MVC is enough

• Think about hypermedia– Especially when the service is publicly available

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Questions

?The presentation and source code will be available

http://msmvps.com/blogs/theproblemsolver/

Excellent rest using asp.net web api

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