1. Embrace HTTP
with ASP.NET Web API
@filip_woj

2. @filip_woj
www.strathweb.com
www.climaxmedia.com
@filip_woj

3. What is ASP.NET Web API?
●
New Microsoft framework (RTM August 2012) for building
HTTP services & applications
●
Aimed at simplyfing and standardizing HTTP area on the
MS stack (see: WCF / ASMX / MVC / HttpHandlers)
●
Supports both REST and RPC style services
●
Open source!
@filip_woj

4. But it's Microsoft!
From: Scott Hanselman's “ONE ASP.NET” talk at aspconf 2012
@filip_woj

5. Web API origins
●
HTTP in WCF
●
WCF REST starter kit
●
WCF Web API
●
finally adopted some concepts from ASP.NET MVC
@filip_woj

6. @filip_woj

7. A mix of WCF Web API & MVC
●
from WCF Web API:
- content negotiation
- message handlers
- REST & dispatching based on HTTP verbs
– code based configuration
@filip_woj

8. A mix of WCF & MVC
●
from MVC:
- model binding concept
- controller based approach & RPC
- routing
- filters
@filip_woj

9. @filip_woj

10. “ASP.NET” “Web API”
●
The name creates lots of misconceptions
●
“ASP.NET”:
it doesn't require neither ASP.NET, nor IIS to run
●
“Web API”:
it's an HTTP framework, that can do much more than "just" API
@filip_woj

11. How can it work without ASP.NET/IIS?
●
Web hosting:
ASP.NET & IIS
OWIN (i.e. Katana)
●
Self hosting: (using WCF hardened core)
WPF
Windows service
console app, any other .NET app
●
Memory hosting: whole pipeline running in memory
@filip_woj

12. @filip_woj

13. OK, but why would I need it?
●
New HTTP object model
●
Work with HTTP concepts
●
HTTP as a fully fledged *application* protocol
●
Facilitates both REST & RPC
●
Async from top-to-bottom
@filip_woj

14. @filip_woj

15. Async examples
●
Handlers:
Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken
cancellationToken);
●
Filters:
Task<HttpResponseMessage> ExecuteActionFilterAsync(HttpActionContext
actionContext, CancellationToken cancellationToken,
Func<Task<HttpResponseMessage>> continuation);
●
Formatters:
Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent
content, TransportContext transportContext);
Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent
content, IFormatterLogger formatterLogger);
@filip_woj

16. New HTTP object model
●
Strongly typed HttpResponseMessage
●
Strongly typed HttpRequestMessage
●
Strongly typed Headers
●
Strongly typed HttpContent
●
No more “angle brackets coding” & magic strings
●
Asynchronous API
●
Client-server symmetry
@filip_woj

17. HTTP status codes
●
1xx – Informational
●
2xx – Successful
●
3xx – Redirection
●
4xx – Error on the client side
●
5xx – Error on the server side
@filip_woj

18. HTTP headers – request
●
Request headers (selected)
– Accept, Accept-Language, Accept-Encoding
– Authorization, Cache-Control, Range
– If-Match, If-Modified-Since, If-Range
●
Content headers (selected)
– Allow, Content-Encoding, Content-Language
– Content-Length, Content-Type, Expires
– Last-Modified
@filip_woj

19. HTTP headers – response
●
Response headers (selected)
– Accept-Ranges, Connection
– Cache-control, Date, Etag
– RetryAfter, Warning, Location
●
Content headers (selected)
– Allow, Content-Encoding, Content-Language
– Content-Length, Content-Type, Expires
– Last-Modified
@filip_woj

20. @filip_woj

21. RPC
●
/api/GetTeams
●
/api/GetTeam?id=1
●
/api/GetPlayersByTeam?id=1
●
/api/AddTeam
●
/api/UpdateTeam
●
/api/UpdateTeam?id=1&name=”Leafs”
●
/api/DeleteTeam?id=1
@filip_woj

22. @filip_woj

23. REST
●
representational state transfer
●
architecture for building systems by Roy Fielding
●
advantages:
stateless
cachability
hypermedia driven (client needs to know one link, usually)
scalability
everything addressable with URI
@filip_woj

24. From: presentation by @alexbeletsky
@filip_woj

25. HTTP verbs
●
Represent CRUD on a resource:
- GET: read, cachable, retreives a resource
- POST: non-cacheable, creates a resource
- PUT: updates a resource, safe to call multiple times
- DELETE: deletes a resource, safe to call multiple times
●
Can also use others i.e. PATCH (partial update of a
resource)
@filip_woj

26. RESTful
●
GET /api/teams
●
GET /api/teams/1
●
GET /api/teams/1/players
●
POST /api/teams
●
PUT /api/teams/1
●
DELETE /api/teams/1
@filip_woj

27. First API – GET
public class TeamsController : ApiController
{
private readonly IUnitOfWork _uow;
public TeamsController(IUnitOfWork uow){
_uow = uow;
}
public IEnumerable<Team> Get()
{
return _uow.Teams;
}
public Team Get(int id)
{
var team = _uow.Teams.FirstOrDefault(i => i.Id == id);
if (team == null) throw new
HttpResponseException(HttpStatusCode.NotFound);
return team;
}
@filip_woj

28. First API – POST
public void Post(Team value)
{
if (!ModelState.IsValid) throw new
HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest,
ModelState));
_uow.Teams.Add(value);
_uow.SaveChanges();
}
@filip_woj

29. First API – PUT
public void Put(int id, Team value)
{
if (!ModelState.IsValid) throw new
HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest,
ModelState));
var team = _uow.Teams.FirstOrDefault(i => i.Id == id);
if (team == null) throw new
HttpResponseException(HttpStatusCode.NotFound);
team.League = value.League;
team.Name = value.Name;
_uow.SaveChanges();
}
@filip_woj

30. First API – DELETE
public void Delete(int id)
{
var team = _uow.Teams.FirstOrDefault(i => i.Id == id);
if (team == null) throw new
HttpResponseException(HttpStatusCode.NotFound);
_uow.Teams.Remove(team);
_uow.SaveChanges();
}
}
@filip_woj

31. Demo: first API
@filip_woj

32. Content negotiation
●
Dynamically deciding the media type
●
Same data can be represented in various formats:
- JSON
– XML
– CSV
– binary
– anything to what your data can be serialized/deserialized from
●
In Web API done with MediaTypeFormatters
@filip_woj

33. Content negotiation in Web API
●
Web API uses the following precedence:
1. MediaTypeMapping
●
/api/resource.json, /api/resource?format=json
2. Accept headers
●
Accept: application/json
3. Content type header
●
Content-Type: text/xml
4. MediaTypeFormatter order & check whether a formatter can
serialize/deserialize a given type
@filip_woj

34. So how my model gets serialized?
●
Out of the box supports:
- XML (DataContractSerializer / XmlSerializer)
- JSON (DataContractSerializer / JSON.NET)
- Form values (from client only, one-way)
@filip_woj

35. Extending content negotiation
●
Very easy, some examples:
- BSON (binary JSON)
- ServiceStack.Text (instead of JSON.NET)
- MessagePack
- Mobi (returning ebook!)
- RSS/Atom
- Supporting Razor views (text/html)
@filip_woj

36. @filip_woj

37. @filip_woj

38. Message Handlers
●
“Russian doll model”
●
run first and last
●
process raw HttpRequestMessage &
HttpResponseMessage
●
Ideal for generic tasks such as authentication or API usage
logging
●
Can be global or route-specific
@filip_woj

39. Client-server symmetry
By: Henrik Frystyk Nielsen
●
Message handlers can run on server and on the client
●
HttpServer is a message handler itself
@filip_woj

40. Filters
●
Conceptually same as in MVC
●
Cached for performance (unlike MVC)
●
Pre-action processing of raw HttpRequestMesage
●
Post-action processing of raw HttpResponseMessage
@filip_woj

41. Controllers
●
Represent your API resources
●
Similar as in MVC
●
Routing engine determines which controller to use
●
Supports nested resources
@filip_woj

42. Dispatching actions
●
By default HTTP verb based (RESTful)
●
Actions matched:
●
by prefix (i.e. GetAll, GetById) or
●
by action attribute (i.e. [HttpPost])
●
Can be changed to action based (RPC style)
@filip_woj

43. @filip_woj

44. Anything else?
●
TDD, BDD – whole pipeline can run in memory
●
Async from top-to-bottom – scales well
●
Simple: figure out your resources, and build around them
●
Next release (Feb 2013) will have OData support
●
Integrates with SignalR
@filip_woj

45. Demo: first API – self hosted
@filip_woj

46. Demo: first API – memory hosted
@filip_woj

47. Demo: adding BSON formatter
@filip_woj

48. Demo: P2P in WPF
@filip_woj

49. Follow these guys
@frystyk
@glennblock
@tourismgeek
@darrel_miller
@aliostad
@benfosterdev
@pwalat
@pmhsfelix
@filip_woj

50. @filip_woj