To create a custom Server-Side HTTP Message Handler in ASP.NET Web API, we need to create a class that must be derived from the System.Net.Http.DelegatingHandler.Step 1 −Create a controller and its corresponding action methods.Exampleusing DemoWebApplication.Models; using System.Collections.Generic; using System.Linq; using System.Web.Http; namespace DemoWebApplication.Controllers{    public class StudentController : ApiController{       List students = new List{          new Student{             Id = 1,             Name = "Mark"          },          new Student{             Id = ... Read More

In a message handler, a series of message handlers are chained together. The first handler receives an HTTP request, does some processing, and gives the request to the next handler. At some point, the response is created and goes back up the chain. This pattern is called a delegating handler.Along with the built-in Server-side Message Handlers, we can also create our own Server-Side HTTP Message Handlers. To create a custom Server-Side HTTP Message Handler in ASP.NET Web API, we make use of DelegatingHandler. We have to create a class deriving from System.Net.Http.DelegatingHandler. That custom class then should override the SendAsync ... Read More

ViewData is a dictionary of objects that are stored and retrieved using strings as keys. It is used to transfer data from Controller to View. Since ViewData is a dictionary, it contains key-value pairs where each key must be a string. ViewData only transfers data from controller to view, not vice-versa. It is valid only during the current request.Storing data in ViewData −ViewData["countries"] = countriesList;Retrieving data from ViewData −string country = ViewData["MyCountry"].ToString();ViewData does not provide compile time error checking. For example, if we mis-spell the key names we wouldn't get any compile time error. We will get to know about ... Read More

Testing WebApi involves sending a request and receiving the response. There are several ways to test the WebApi. Here we will test the WebApi using postman and swagger. Let us create a StudentController like below.Student Modelnamespace DemoWebApplication.Models{    public class Student{       public int Id { get; set; }       public string Name { get; set; }    } }Student ControllerExampleusing DemoWebApplication.Models; using System.Collections.Generic; using System.Linq; using System.Web.Http; namespace DemoWebApplication.Controllers{    public class StudentController : ApiController{       List students = new List{          new Student{             ... Read More

HttpClient class provides a base class for sending/receiving the HTTP requests/responses from a URL. It is a supported async feature of .NET framework. HttpClient is able to process multiple concurrent requests. It is a layer over HttpWebRequest and HttpWebResponse. All methods with HttpClient are asynchronous. HttpClient is available in System.Net.Http namespace.Let us create an WebAPI application having a StudentController and respective action methods.Student Modelnamespace DemoWebApplication.Models{    public class Student{       public int Id { get; set; }       public string Name { get; set; }    } }Student Controllerusing DemoWebApplication.Models; using System.Collections.Generic; using System.Linq; using System.Web.Http; ... Read More

Authorization is the process of deciding whether the authenticated user is allowed to perform an action on a specific resource (Web API Resource) or not. For example, having the permission to get data and post data is a part of authorization. The Authorization Process happens before executing the Controller Action Method which provides you the flexibility to decide whether we want to grant access to that resource or not.In ASP.NET Web API authorization is implemented by using the Authorization filters which will be executed before the controller action method executed. Web API provides a built-in authorization filter, AuthorizeAttribute. This filter ... Read More

Content negotiation is the process of selecting the best representation for a given response when there are multiple representations available. Means, depending on the Accept header value in the request, the server sends the response. The primary mechanism for content negotiation in HTTP are these request headers −Accept − Which media types are acceptable for the response, such as "application/json, " "application/xml, " or a custom media type such as "application/vnd.example+xml"Accept-Charset − Which character sets are acceptable, such as UTF-8 or ISO 8859-1.Accept-Encoding − Which content encodings are acceptable, such as gzip.Accept-Language − The preferred natural language, such as "en-us".The ... Read More

Child Action is only accessible by a child request. It will not respond to the URL requests. If an attempt is made, a runtime error will be thrown stating - Child action is accessible only by a child request. Child action methods can be invoked by making child request from a view using Action() and RenderAction() html helpers.Child action methods are different from NonAction methods, in that NonAction methods cannot be invoked using Action() or RenderAction() helpers.Below is the Child Action Error when we try to invoke it using URL.ControllerExampleusing System.Collections.Generic; using System.Web.Mvc; namespace DemoMvcApplication.Controllers{    public class HomeController : ... Read More

In an ASP .Net MVC application filters can be applied in three levels.Action Method LevelController LevelGlobal LevelAction Method LevelFilters that are applied at the Action Method level will work only particularly for that action method.using System.Web.Mvc; namespace DemoMvcApplication.Controllers{    public class HomeController : Controller{       [Authorize] //Action Method Level       public string Index(){          return "Index Invoked";       }    } }Controller LevelController level filters are applied to all the action methods. The following filter are applicable to all the action methods of the HomeController, but not on other controllers.using System.Web.Mvc; ... Read More

The ASP.Net MVC Routing module is responsible for mapping incoming browser requests to particular MVC controller actions. When the ASP.NET MVC application launches then the application registers one or more patterns with the framework's route table to tell the routing engine what to do with any requests that matches those patterns. When the routing engine receives a request at runtime, it matches that request's URL against the URL patterns registered with it and gives the response according to a pattern match.ASP.NET introduced Routing to eliminate the needs of mapping each URL with a physical file. Routing enables us to define ... Read More