ASP.NET Web API

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  • 1. Contents  What & Why ASP.NET Web API  A look at Rest & Soap  Basic Web API Structure  Web API Routing & Actions  Validation  Odata  Content Negotiation  Http Client
  • 2. ASP.NET Web API  ASP.NET Web API is a framework for building http based services in top of .net framework.  WCF  Care about transport flexibility.  WebAPI  Care about HTTP
  • 3. Build Richer Apps Reach More Clients
  • 4.  Reach more clients  Client appropriate format  Embrace http  Use http as an application protocol  Amazon has both Rest and Soap based services and 85% of the usage is Rest based.
  • 5.  SOAP  A specification  Rest  A set of architectural principal  Resource Oriented Architecture  Resources  Their names(URIs)  Uniform Intercace
  • 6.  Asmx  Ws*  Wcf  Wcf 3.5  Wcf rest starter kit  Wcf Rest service  ASP.Net Web API
  • 7. Web API - 1 slide public class ValueController : ApiController { // GET <controller> public string Get() { return "Demo result at " + DateTime.Now.ToString(); } } protected void Application_Start(object sender, EventArgs e) { GlobalConfiguration.Configuration.Routes.Add("default", new HttpRoute("{controller}")); }
  • 8. Demo
  • 9. Microsoft /web ® Sample Read-only Model and Controller
  • 10. Microsoft /web ® Read-only Controller Actions to return data
  • 11. Microsoft /web ® Routing a Web API Using Global.asax.cs
  • 12. Routing and Actions  Web API uses the HTTP method, not the URI path, to select the action.  To determine which action to invoke, the framework uses a routing table. routes.MapHttpRoute( name: "API Default", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } );
  • 13.  If no route matches, the client receives a 404 error.  Custom name mapping to http actions. [HttpGet] public Product FindProduct(id) {}
  • 14.  or can override the action name by using the ActionName attribute.  api/products/thumbnail/id [HttpGet] [ActionName("Thumbnail")] public HttpResponseMessage GetThumbnailImage(int id);
  • 15.  To prevent a method from getting invoked as an action, use the NonAction attribute. // Not an action method. [NonAction] public string GetPrivateData() { ... }
  • 16. Exception Handling  By default, most exceptions are translated into an HTTP response with status code 500, Internal Server Error. public Product GetProduct(int id) { Product item = repository.Get(id); if (item == null) { var resp = new HttpResponseMessage(HttpStatusCode.NotFound) { Content = new StringContent(string.Format("No product with ID = {0}", id)), } throw new HttpResponseException(resp); } return item; }
  • 17.  HTTP/1.1 404 Not Found Content-Type: application/json; charset=utf-8 Date: Thu, 09 Aug 2012 23:27:18 GMT Content-Length: 51 { "Message": “No product with id = 12 not found" }
  • 18.  You can customize how Web API handles exceptions by writing an exception filter. public class NotImplExceptionFilterAttribute : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Exception is NotImplementedException) { context.Response = new HttpResponseMessage(HttpStatusCode.NotImplemented); } } }
  • 19. There are several ways to register a Web API exception filter:  By action  By controller  Globally [NotImplExceptionFilter] GlobalConfiguration.Configuration.Filters.Add( new ProductStore.NotImplExceptionFilterAttribute());
  • 20. Validation  public class Product { public int Id { get; set; } [Required] public string Name { get; set; } public decimal Price { get; set; } [Range(0,999)] public double Weight { get; set; } }
  • 21.  if (ModelState.IsValid) { return new HttpResponseMessage(HttpStatusCode.OK); } else { return new HttpResponseMessage(HttpStatusCode.BadReques t); }
  • 22.  public class ModelValidationFilterAttribute : ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext actionContext) { if (actionContext.ModelState.IsValid == false) { var errors = new Dictionary<string, IEnumerable<string>>(); foreach (KeyValuePair<string, ModelState> keyValue in actionContext.ModelState) { errors[keyValue.Key] = keyValue.Value.Errors.Select(e => e.ErrorMessage); } actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.BadReq uest, errors); } } }
  • 23.  HTTP/1.1 400 Bad Request Server: ASP.NET Development Server/10.0.0.0 Date: Fri, 20 Jul 2012 21:42:18 GMT Content-Type: application/json; charset=utf-8 Content-Length: 239 Connection: Close { "product": [ "Required property 'Name' not found in JSON. Line 1, position 18." ], "product.Name": [ "The Name field is required." ], "product.Weight": [ "The field Weight must be between 0 and 999." ] }
  • 24.  GlobalConfiguration.Configuration.Filters.Add(new ModelValidationFilterAttribute());  [ModelValidationFilter]
  • 25.  public class Product { public string Name { get; set; } public decimal Price { get; set; } [JsonIgnore] public int ProductCode { get; set; } // omitted }
  • 26.  [DataContract] public class Product { [DataMember] public string Name { get; set; } [DataMember] public decimal Price { get; set; } public int ProductCode { get; set; } // omitted by default }
  • 27. OData http://localhost/Products?$orderby=Name The EnableQuerySupport method enables query options gloablly for any controller action that returns anIQueryable type.  To enable only for specific action/controller [Queryable] IQueryable<Product> Get() {}
  • 28. Option Description $filter Filters the results, based on a Boolean condition. $inlinecount Tells the server to include the total count of matching entities in the response. (Useful for server-side paging.) $orderby Sorts the results. $skip Skips the first n results. $top Returns only the first n the results. :
  • 29.  http://localhost/odata/Products?$orderby=Category, Price desc [Queryable(PageSize=10)] public IQueryable<Product> Get() { return products.AsQueryable(); } [Queryable(AllowedQueryOptions= AllowedQueryOptions.Skip | AllowedQueryOptions.Top)]
  • 30. Demo
  • 31. Content Negotiation  The process of selecting the best representation for a given response when there are multiple representations available.  Accept:  Accept-Charset:  Accept-Language:  Accept-Encoding:
  • 32. HttpClient  HttpClient is a modern HTTP client for ASP.NET Web API. It provides a flexible and extensible API for accessing all things exposed through HTTP.  HttpClient is the main class for sending and receiving HttpRequestMessages and HttpResponseMessages.  Task based pattern  Same HttpClient instance can be used for multiple URIs even from different domains.
  • 33. Demo
  • 34. Self Reading  Authentication and Authorization  Extensibility  Tracing and Debugging
  • 35. Thanks