ASP.NET Web API
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This document provides an overview of ASP.NET Web API, a framework for building HTTP-based services. It discusses key Web API concepts like REST, routing, actions, validation, OData, content negotiation, and the HttpClient. Web API allows building rich HTTP-based apps that can reach more clients by embracing HTTP standards and using HTTP as an application protocol. It focuses on HTTP rather than transport flexibility like WCF.
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ASP.NET Web API
- 2. 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
- 3. 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
- 4. Build Richer Apps Reach More Clients
- 5. 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.
- 7. SOAP A specification Rest A set of architectural principal Resource Oriented Architecture Resources Their names(URIs) Uniform Intercace
- 10. Asmx Ws* Wcf Wcf 3.5 Wcf rest starter kit Wcf Rest service ASP.Net Web API
- 11. 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}")); }
- 12. Demo
- 13. Microsoft /web ® Sample Read-only Model and Controller
- 14. Microsoft /web ® Read-only Controller Actions to return data
- 15. Microsoft /web ® Routing a Web API Using Global.asax.cs
- 16. 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 } );
- 17. If no route matches, the client receives a 404 error. Custom name mapping to http actions. [HttpGet] public Product FindProduct(id) {}
- 18. or can override the action name by using the ActionName attribute. api/products/thumbnail/id [HttpGet] [ActionName("Thumbnail")] public HttpResponseMessage GetThumbnailImage(int id);
- 19. To prevent a method from getting invoked as an action, use the NonAction attribute. // Not an action method. [NonAction] public string GetPrivateData() { ... }
- 20. 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; }
- 21. 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" }
- 22. 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); } } }
- 23. There are several ways to register a Web API exception filter: By action By controller Globally [NotImplExceptionFilter] GlobalConfiguration.Configuration.Filters.Add( new ProductStore.NotImplExceptionFilterAttribute());
- 24. 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; } }
- 25. if (ModelState.IsValid) { return new HttpResponseMessage(HttpStatusCode.OK); } else { return new HttpResponseMessage(HttpStatusCode.BadReques t); }
- 26. 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); } } }
- 27. 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." ] }
- 29. public class Product { public string Name { get; set; } public decimal Price { get; set; } [JsonIgnore] public int ProductCode { get; set; } // omitted }
- 30. [DataContract] public class Product { [DataMember] public string Name { get; set; } [DataMember] public decimal Price { get; set; } public int ProductCode { get; set; } // omitted by default }
- 31. 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() {}
- 32. 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. $top Returns only the first n the results. :
- 33. http://localhost/odata/Products?$orderby=Category, Price desc [Queryable(PageSize=10)] public IQueryable<Product> Get() { return products.AsQueryable(); } [Queryable(AllowedQueryOptions= AllowedQueryOptions.Skip | AllowedQueryOptions.Top)]
- 34. Demo
- 35. 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:
- 36. 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.
- 37. Demo
- 38. Self Reading Authentication and Authorization Extensibility Tracing and Debugging
- 39. Thanks