The DefaultHttpControllerSelector class in web api is responsible for selecting the appropriate controller action method that we send in the URI.Say we have to implement versioning in the query string like belowv=1 StudentsV1Controller (Version 1) v=2 StudentsV2Controller (Version 2)If we pass the versioning information in the query string like http://localhost:58174/api/student?v=1 will result in 404 Not Found error response because the SelectController() method which is present in DefaultHttpControllerSelector will look for the StudentsController but we have only StudentsV1Controller and StudentsV2Controller.To handle this case, we should add our own CustomControllerSelector which implements the DefaultHttpControllerSelector class.CustomControllerSelector −Exampleusing System.Net.Http; using System.Web; using System.Web.Http; using ... Read More

Once a Web API service is made public, different client applications start using our Web API services. As the business grows and requirements change, we may have to change the services as well, but the changes to the services should be done in way that does not break any existing client applications.This is when Web API versioning helps. We keep the existing services as is, so we are not breaking the existing client applications, and develop a new version of the service that new client applications can start using.One of the option to implement versioning is by using URI. Below ... Read More

The HTTP verbs comprise a major portion of our “uniform interface” constraint and provide us the action counterpart to the noun-based resource. The primary or mostcommonly-used HTTP verbs (or methods, as they are properly called) are POST, GET, PUT, PATCH, and DELETE. These correspond to create, read, update, and delete (or CRUD) operations, respectively. There are a number of other verbs, too, but are utilized less frequently. Of those less-frequent methods, OPTIONS and HEAD are used more often than others.Action method can be named as HTTP verbs like Get, Post, Put, Patch or Delete. However, we can append any suffix ... Read More

A public method in a controller is called an Action method. Let us consider an example where DemoController class is derived from ApiController and includes multiple action methods whose names match with HTTP verbs like Get, Post, Put and Delete.Examplepublic class DemoController : ApiController{    public IHttpActionResult Get(){       //Some Operation       return Ok();    }    public IHttpActionResult Post([FromUri]int id){       //Some Operation       return Ok();    }    public IHttpActionResult Put([FromUri]int id){       //Some Operation       return Ok();    }    public IHttpActionResult Delete(int id){   ... Read More

Filters are used to inject extra logic at the different levels of WebApi Framework request processing. Filters provide a way for cross-cutting concerns (logging, authorization, and caching). Filters can be applied to an action method or controller in a declarative or programmatic way. Below are the types of filters in Web API C#.Authentication Filter −An authentication filter helps us to authenticate the user detail. In the authentication filter, we write the logic for checking user authenticity.Authorization Filter −Authorization Filters are responsible for checking User Access. They implement the IAuthorizationFilterinterface in the framework.Action Filter −Action filters are used to add extra ... Read More

Cross-Origin Resource Sharing (CORS) is a mechanism that uses additional HTTP headers to tell browsers to give a web application running at one origin, access to selected resources from a different origin. A web application executes a cross-origin HTTP request when it requests a resource that has a different origin (domain, protocol, or port) from its own.For example, let us consider an application which is having its front end (UI) and back end (Service). Say the front-end is served from https://demodomain-ui.com and the backend is served from from https://demodomain-service.com/api. If an end user tries to access the application, for security ... Read More

We can create our own custom class as a result type by implementing IHttpActionResult interface. IHttpActionResult contains a single method, ExecuteAsync, which asynchronously creates an HttpResponseMessage instance.public interface IHttpActionResult {    Task ExecuteAsync(CancellationToken    cancellationToken); }If a controller action returns an IHttpActionResult, Web API calls the ExecuteAsync method to create an HttpResponseMessage. Then it converts the HttpResponseMessage into an HTTP response message.ExampleTo have our own custom result we must create a class that implements IHttpActionResult interface.using System.Net.Http; using System.Threading; using System.Threading.Tasks; using System.Web.Http; namespace DemoWebApplication.Controllers{    public class CustomResult : IHttpActionResult{       string _value;       HttpRequestMessage _request; ... Read More

The Web API action method can have following return types.VoidPrimitive Type/Complex TypeHttpResponseMessageIHttpActionResultVoid −It's not necessary that all action methods must return something. It can have void return type.Exampleusing DemoWebApplication.Models using System.Web.Http; namespace DemoWebApplication.Controllers{    public class DemoController : ApiController{       public void Get([FromBody] Student student){          //Some Operation       }    } }The action method with void return type will return 204 No Content response.Primitive Type/Complex Type −The action method can return primitive type like int, string or complex type like List etc.Exampleusing DemoWebApplication.Models; using System.Collections.Generic; using System.Web.Http; namespace DemoWebApplication.Controllers{    public class ... Read More

When the ASP.NET Web API calls a method on a controller, it must set values for the parameters, a process called parameter binding.In order to bind a model (an action parameter), that would normally default to a formatter, from the URI we need to decorate it with [FromUri] attribute. FromUriAttribute simply inherits from ModelBinderAttribute, providing us a shortcut directive to instruct Web API to grab specific parameters from the URI using the ValueProviders defined in the IUriValueProviderFactory. The attribute itself is sealed and cannot be extended any further, but you add as many custom IUriValueProviderFactories as you wish.The [FromBody] attribute ... Read More

The Task.WaitAll blocks the current thread until all other tasks have completed execution. The Task.WhenAll method is used to create a task that will complete if and only if all the other tasks have completed.If we are using Task.WhenAll we will get a task object that isn’t complete. However, it will not block but will allow the program to execute. On the contrary, the Task.WaitAll method call actually blocks and waits for all other tasks to complete.To understand with an example, let us say we have a task that performs some activity with the UI thread say some animation needs ... Read More