• Extension to the Windows Communication Foundation
• Announced at the 2010 PDC
  • Work in progress - currently in Preview 4
  • No final release date yet
• Community participation
  • Feedback
  • However, no source code contribution

• Development of web APIs, characterized by
  • Usage of HTTP as the application protocol (no SOAP)
  • Usage of multiple media types
  • Usage of multiple formats (e.g. XML, JSON)
  • Multiple architectural styles (e.g. RPC and ReST)
  • Consumption by multiple client devices
    
• Base for ReST style system
  • Not "opinionated"
  • No resource model yet

• Testability
  • E.g. No need for WebOperationContext.Current
  • E.g. Public constructors
• Composability
  • IOC/DI friendly
    
• Simpler configuration model
  • Code based

• Source available at wcf.codeplex.com
  • hg clone https://hg01.codeplex.com/wcf
    
• Nuget package
  • Install-Package WebApi.All

• Original WCF programming model
  • Based on the SOAP and WSDL models
  • Transport independence
  • HTTP is a transport detail
    
• Web API programming model
  • Based on the HTTP model
    
  • HTTP used as the application level protocol
  • Adds on the WCF original model

 1 [ServiceContract]
 2 class TheService
 3 {
 4     [WebGet(UriTemplate = "time")]
 5     HttpResponseMessage TheOperation(HttpRequestMessage req)
 6     {
 7         return new HttpResponseMessage()
 8         {
 9             StatusCode = HttpStatusCode.OK,
10             Content = new StringContent(
11                 DateTime.Now.ToLongTimeString())
12         };
13     }
14 }

• ServiceContract is just a container for operations
• Operations are instance methods annotated with
  • WebGet[UriTemplate="..."], or
  • WebInvoke[UriTemplate="...", Method="..."]
• Operations handle HTTP requests selected by
  • The HTTP method (e.g. GET, POST)
  • The match between the Request URI and the URI template
• Contract is a legacy term

• Strongly typed request and response messages
  
• With public constructors

• HttpRequestMessage
• HttpRequestMessage<T>
• URI template match bound variables
  • E.g. UriTemplate = "time/{zone}"
• Query string pairs
• A content model
• Parameters injected by operation handlers

• HttpResponseMessage
• HttpRespondeMessage<T>
• A content model

 1 class Program
 2 {
 3     static void Main(string[] args)
 4     {
 5         using (var host = new HttpServiceHost(typeof(TheService), 
 6             "http://localhost:8080"))
 7         {
 8             host.Open();
 9             Console.WriteLine("Host opened at {0} , press any key to end", 
10                 host.Description.Endpoints[0].Address);
11             Console.ReadKey();
12         }
13     }
14 }

• Similar to the original WCF model
  • service hosts and factories
• Self-hosting
  • New HttpServiceHost
  • New HttpBinding
• IIS hosting
  • RouteCollection extension methods

1 public class Global : System.Web.HttpApplication
2 {
3     protected void Application_Start(object sender, EventArgs e)
4     {
5         RouteTable.Routes.MapServiceRoute<TheService>("base_path");
6     }
7 }

• Message Handlers
  • Receive a HttpRequestMessage
  • Must produce a HttpResponseMessage asynchronosly
  • Contains a reference to an inner channel
  • Endpoint scoped
• Operation Handlers
  • Receive HttpParameter sets
  • Produce HttpParameter sets
  • Operation scoped

• Operation Handlers
  • Use parameters from a bag
  • Contribute with parameters to the same bag
    
• Initially this bag contains
  • The HttpRequestMessage
  • The matched URITemplate bound variables
• The final bag contents are usable by the operation

• Operations can receive HttpRequestMessage<T> or a content model
• Operations can return `HttpRequestMessage<T> or a content model
• MediaTypeFormatter - conversion between the HTTP body and the content model
• Supports server-driven content negotiation

• In prototyping phase
• HttpHostConfiguration configuration builder
  • Fluent interface
• HttpConfigurableServiceHost service host
• RouteCollection extension methods receiving the configuration

 1 var cfg = HttpHostConfiguration.Create()
 2     .AddMessageHandlers(typeof (SampleMessageHandler))
 3     .SetOperationHandlerFactory(new MyOperationConfigurationFactory());
 4 
 5 var host = new HttpConfigurableServiceHost(..., cfg, ...){
 6 
 7 class MyOperationConfigurationFactory : HttpOperationHandlerFactory{
 8     override Collection<HttpOperationHandler> 
 9     OnCreateRequestHandlers(
10         ServiceEndpoint endpoint, 
11         HttpOperationDescription operation){
12         var coll = base.OnCreateRequestHandlers(endpoint, operation);
13         coll.Add(new LoggingOperationHandler(operation));
14         if (operation.Name == "GetTimeString")
15         {
16             Formatters.Remove(Formatters.XmlFormatter);
17             Formatters.Remove(Formatters.JsonFormatter);
18             Formatters.Add(new WaveFromTextFormatter());
19             Formatters.Add(new ImageFromTextFormatter());
20         }
21         return coll;
22     }
23 }

• http://wcf.codeplex.com/, namely the source and the discussions
• Glenn Block's blog and videos
• My WCF Web API post series