1. Unleash
the power of HTTP
with ASP
.NET Web API
@filip_woj

2. @filip_woj
www.strathweb.com
www.arcmedia.ch
@filip_woj

3. HTTP
@filip_woj

4. Trying to build a good API
@filip_woj

5. What is ASP
.NET Web API?


New Microsoft framework (August 2012, Version 2
October 2013) for building HTTP services & applications
Aimed at simplyfing and standardizing HTTP area on the
MS stack (see: WCF / ASMX / MVC / HttpHandlers)

HTTP as a fully fledged *application* protocol

Async from top-to-bottom

Open source!
@filip_woj

8. “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

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

11. Demo: first API – self hosted
@filip_woj

12. 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

13. HTTP status codes

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

16. Demo: Created 201 / BadRequest 400
@filip_woj

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

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

20. 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. From: presentation by @alexbeletsky

23. HTTP verbs

Represent core operations 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

24. 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

25. Much better
@filip_woj

26. Controllers

Represent your API resources

Similar as in MVC

Routing engine determines which controller to use

Web API 2 introduces attribute routing

Supports nested resources
@filip_woj

27. 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

28. Don’t be scared of REST
@filip_woj

29. 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

30. 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

31. Demo: Not Acceptable 406
@filip_woj

32. 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

34. 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

35. Sample Handler

36. Demo: Memory hosted
@filip_woj

37. @filip_woj