Microsoft /web

®

ASP.NET Web API

Fahad AslamHabib Ullah

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

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

Build Richer AppsReach More Clients

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.

SOAP A specification

Rest A set of architectural principal

Resource Oriented Architecture Resources Their names(URIs) Uniform Intercace

Asmx Ws* Wcf Wcf 3.5 Wcf rest starter kit Wcf Rest service ASP.Net Web API

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}"));

}

Demo

Microsoft /web

®

Sample Read-only Model and Controller

public class Person{ public int Id { get; set; } public string Name { get; set; }}

Step 1:Create a Model

public class PersonController : ApiController{ List<Person> _people; public PersonController() { _people = new List<Person>(); _people.AddRange(new Person[] { new Person { Id = 1, Name = "Chuck Norris" }, new Person { Id = 2, Name = "David Carradine" }, new Person { Id = 3, Name = "Bruce Lee" } }); }}

Step 2:Make an API Controller

Microsoft /web

®

Read-only Controller Actions to return data

// GET /api/personpublic IEnumerable<Person> Get(){ return _people;}

Step 3:Return everything

// GET /api/person/5public Person Get(int id){ return _people.First(x => x.Id == id);}

Step 4:Return one item

Microsoft /web

®

Routing a Web API Using Global.asax.cs

public static void RegisterRoutes(RouteCollection routes){ routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } );}

Routing:Familiar syntax, conventional approach

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 });

If no route matches, the client receives a 404 error.

Custom name mapping to http actions.

[HttpGet]    public Product FindProduct(id) {}

or can override the action name by using the ActionName attribute.

api/products/thumbnail/id[HttpGet]    [ActionName("Thumbnail")]    public HttpResponseMessage GetThumbnailImage(int id);

To prevent a method from getting invoked as an action, use the NonAction attribute.

// Not an action method.[NonAction]  public string GetPrivateData() { ... }

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;}

HTTP/1.1 404 Not FoundContent-Type: application/json; charset=utf-8Date: Thu, 09 Aug 2012 23:27:18 GMTContent-Length: 51

{  "Message": “No product with id = 12 not found"}

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);            }        }    }

There are several ways to register a Web API exception filter: By action By controller Globally

[NotImplExceptionFilter]

GlobalConfiguration.Configuration.Filters.Add(    new ProductStore.NotImplExceptionFilterAttribute());

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; }}

if (ModelState.IsValid)        {            return new HttpResponseMessage(HttpStatusCode.OK);        }        else        {            return new HttpResponseMessage(HttpStatusCode.BadRequest);        }

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.BadRequest, errors);        }    }}

HTTP/1.1 400 Bad RequestServer: ASP.NET Development Server/10.0.0.0Date: Fri, 20 Jul 2012 21:42:18 GMTContent-Type: application/json; charset=utf-8Content-Length: 239Connection: 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."  ]}

GlobalConfiguration.Configuration.Filters.Add(new ModelValidationFilterAttribute());

[ModelValidationFilter]

public class Product{    public string Name { get; set; }    public decimal Price { get; set; }    [JsonIgnore]    public int ProductCode { get; set; } // omitted}

[DataContract]public class Product{    [DataMember]    public string Name { get; set; }    [DataMember]    public decimal Price { get; set; }    public int ProductCode { get; set; }  // omitted by default}

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() {}

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.

:

http://localhost/odata/Products?$orderby=Category,Price desc

[Queryable(PageSize=10)]public IQueryable<Product> Get() {    return products.AsQueryable();}

[Queryable(AllowedQueryOptions=    AllowedQueryOptions.Skip | AllowedQueryOptions.Top)]

Demo

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:

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.

Demo

Self Reading Authentication and Authorization Extensibility Tracing and Debugging

Thanks