Web API in ASP.net MVC

Web API

Web API is a platform for building Restful Services. 

Rest - Representational state transfer

Rest is a simple way of sending and receiving data between client and server and it doesn't have very many standards defined. You can send and receive data as JSON, XML or even plain text. Its light weighted compared to SOAP.

Web API supports different formats of response data. Built-in support for JSON, XML format.

Restful service is nothing but design pattern.

Url based application developed by Web APi only

Web api give the URl based on url when hit the Url to get the response. That particular response access by PHP, .NET, JAVA any other technology or any other application access by it. 

Web api have a structure in the form of mvc (Model View Controller).

In our web Api will not have any concept of views, we have a model & controller, but views are nothing but url what your going to get it.

In WEB API Controllers do not return views, only part of Model and Controller.  

WEB API Controller: 

The following is a simple controller class added by visual studio by default when we created a new Web API project in the Create WEB API Project section. 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Net;

using System.Net.Http;

using System.Web.Http;

namespace Asp.net_WebApi.Controllers

{

    public class ValuesController : ApiController

   {

        // GET api/values

        public IEnumerable<string> Get()

        {

            return new string[] { "value1", "value2" };

        }

        // GET api/values/5

        public string Get(int id)

        {

            return "value";

        }

        // POST api/values

        public void Post([FromBody]string value)

        {

        }

        // PUT api/values/5

        public void Put(int id, [FromBody]string value)

        {

        }

        // DELETE api/values/5

        public void Delete(int id)

        {

        }

    }

} 

As you can see in the above example, ValuesController class is derived from ApiController and includes multiple action methods whose names match with HTTP verbs like Get, Post, Put and Delete 

Whenever you create web api methods by using prefix of HTTP verbs. 

Difference between ApiController and Controller

• Web ApiController is Derives from System.Web.Http.ApiController class

      Ex : public class ValuesController : ApiController

      {

      }

• MVC Controller is Derives from System.Web.Mvc.Controller class.

       Ex: public class EmployeeController : Controller  

      {

      }

• Web Api Controller return data

• MVC Controller return View 

• Web Api Controller Method name must start with Http verbs otherwise apply http verbs attribute.

• MVC Controller Must apply appropriate Http verbs attribute like HttpGet, HttpPost 

How to access web api controller in asp.net mvc project 

Go through ur project (Asp.net WebApi) -> App_Start -> WebApiConfig.cs file

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web.Http; 

namespace Asp.net_WebApi

{

    public static class WebApiConfig

    {

        public static void Register(HttpConfiguration config)

        {

            // Web API configuration and services

            // Web API routes

            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(

                name: "DefaultApi",

                routeTemplate: "api/{controller}/{id}",

                defaults: new { id = RouteParameter.Optional }

            );

        }

    }

}

We can access through api/Controller

We can’t deal with action method directly. 

When u build the web api application it shows like below:

The above page comes from home control -> index.cshtml page it’s shows  

<div class="jumbotron">

    <h1>ASP.NET</h1>

    <p class="lead">ASP.NET is a free web framework for building great Web sites and Web applications using HTML, CSS, and JavaScript.</p>

    <p><a href="https://asp.net" class="btn btn-primary btn-lg">Learn more &raquo;</a></p>

</div>

<div class="row">

    <div class="col-md-4">

        <h2>Getting started</h2>

        <p>ASP.NET Web API is a framework that makes it easy to build HTTP services that reach

        a broad range of clients, including browsers and mobile devices. ASP.NET Web API

        is an ideal platform for building RESTful applications on the .NET Framework.</p>

        <p><a class="btn btn-default" href="https://go.microsoft.com/fwlink/?LinkId=301870">Learn more &raquo;</a></p>

    </div>

    <div class="col-md-4">

        <h2>Get more libraries</h2>

        <p>NuGet is a free Visual Studio extension that makes it easy to add, remove, and update libraries and tools in Visual Studio projects.</p>

        <p><a class="btn btn-default" href="https://go.microsoft.com/fwlink/?LinkId=301871">Learn more &raquo;</a></p>

    </div>

    <div class="col-md-4">

        <h2>Web Hosting</h2>

        <p>You can easily find a web hosting company that offers the right mix of features and price for your applications.</p>

        <p><a class="btn btn-default" href="https://go.microsoft.com/fwlink/?LinkId=301872">Learn more &raquo;</a></p>

    </div>

</div>

How to get API link in above output screen

Go through ur project like Asp.net WebApi -> Areas -> Controllers -> HelpController.cs page

using System;

using System.Web.Http;

using System.Web.Mvc;

using Asp.net_WebApi.Areas.HelpPage.ModelDescriptions;

using Asp.net_WebApi.Areas.HelpPage.Models;

namespace Asp.net_WebApi.Areas.HelpPage.Controllers

{

    /// <summary>

    /// The controller that will handle requests for the help page.

    /// </summary>

    public class HelpController : Controller

    {

        private const string ErrorViewName = "Error";

        public HelpController()

            : this(GlobalConfiguration.Configuration)

        {

        }

        public HelpController(HttpConfiguration config)

        {

            Configuration = config;

        }

        public HttpConfiguration Configuration { get; private set; }

        public ActionResult Index()

        {

            ViewBag.DocumentationProvider = Configuration.Services.GetDocumentationProvider();

            return View(Configuration.Services.GetApiExplorer().ApiDescriptions);

        }

        public ActionResult Api(string apiId)

        {

            if (!String.IsNullOrEmpty(apiId))

            {

                HelpPageApiModel apiModel = Configuration.GetHelpPageApiModel(apiId);

                if (apiModel != null)

                {

                    return View(apiModel);

                }

            }

            return View(ErrorViewName);

        }

        public ActionResult ResourceModel(string modelName)

        {

            if (!String.IsNullOrEmpty(modelName))

            {

                ModelDescriptionGenerator modelDescriptionGenerator = Configuration.GetModelDescriptionGenerator();

                ModelDescription modelDescription;

                if (modelDescriptionGenerator.GeneratedModels.TryGetValue(modelName, out modelDescription))

                {

                    return View(modelDescription);

                }

            }

            return View(ErrorViewName);

        }

    }

}

This page will generate links for us like below 

Note: Don't Change above code. 

If changed method name in ValuesController.cs page like below

       // GET api/values

        public IEnumerable<string> AGet()

        {

            return new string[] { "value1", "value2" };

        }

Now run the application the output show like below

In above output screen Get and Post Method are not visible in value section, because we add A before GET method. So, don’t write before GET method. The methods start with HTTP Verbs only (Get, Post, Put, Delete).

If you want to change method name u can add after Http Verbs like GetA.

       // GET api/values

        public IEnumerable<string> GetA()

        {

            return new string[] { "value1", "value2" };

        }

How many Get methods we can define in Web Api controller?

According to user requirement we can define no of get method in web api controller. The controller is a class so, in class we define no.of methods.

But, we can define same type of method without parameter in ValueController.cs page like below

        // GET api/values

        public IEnumerable<string> GetA()

        {

            return new string[] { "value1", "value2" };

        }

       // GET api/values

        public IEnumerable<string> GetB()

        {

            return new string[] { "B1", "B2" };

        }

In above output Value section, we miss Get methods, if you want those method we can use route concept.

Web API Routing:

Web API routing is similar to ASP.NET Routing. It routes an incoming HTTP request to a particular action method on a Web API controller.

Web API supports two types of routing:

1. Attribute Routing

2. Convention-based Routing

Attribute Routing:

Place on a controller or action to expose it directly via a route. 

When u have same methods and same parameter in that time we use attribute base routing.

If you want to get through method you define Route like below

  // GET api/values

        public IEnumerable<string> GetA()

        {

            return new string[] { "value1", "value2" };

        }

       // GET api/values

        [Route("GetEmployee")]

        public IEnumerable<string> GetB()

        {

            return new string[] { "B1", "B2" };

        }

When you see two square bracket ([]) are there inside u write anything that is called as attribute.

the above output it's add two more Get methods because u add 

[Route("GetEmployee")]

that means we define two different method name and same Patten in that time we can use route method.

when u call GetEmployee (https://localhost:44387/GetEmployee)  it will display output like below:

<ArrayOfstring xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/2003/10/Serialization/Arrays">

<string>B1</string>

<string>B2</string>

</ArrayOfstring>

I get B1 and B2 string

Now I define one more method in ValueController.cs page like below: 

        // GET api/values

        public IEnumerable<string> GetA()

        {

            return new string[] { "value1", "value2" };

        }

        [Route("GetEmployee")]

        public IEnumerable<string> GetB()

        {

            return new string[] { "B1", "B2" };

        }

        [Route("GetEmployeeInfo")]

        public IEnumerable<string> Getc()

        {

            return new string[] { "B1", "B2" };

        }

 when you build the application it's show like below

 Incase if you want to define URL base, you define like below in your ValueController.cs page. 

        // GET api/values

        public IEnumerable<string> GetA()

        {

            return new string[] { "value1", "value2" };

        }

        [Route("api/Values/GetEmployee")]

        public IEnumerable<string> GetB()

        {

            return new string[] { "B1", "B2" };

        }

        [Route("api/Values/GetEmployeeInfo")]

        public IEnumerable<string> Getc()

        {

            return new string[] { "B1", "B2" };

        }

 when you build the application it's show like below

But any controller (valueController.cs page) we can define no of method. if you create static url, incase if you want to change the url we go each and every method then change. it's a time taking Processes that way RoutePrefix came into picture. 

RoutePrefix:

A controller with a route prefix that applies to all actions within the controller

It's means before attribute routing

now we can change like below in ValueController.cs page. 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Net;

using System.Net.Http;

using System.Web.Http;

namespace Asp.net_WebApi.Controllers

{

    [RoutePrefix("api/Values")]

    public class ValuesController : ApiController

    {

        // GET api/values

        public IEnumerable<string> GetA()

        {

            return new string[] { "value1", "value2" };

        }

        [Route("GetEmployee")]

        public IEnumerable<string> GetB()

        {

            return new string[] { "B1", "B2" };

        }

        [Route("GetEmployeeInfo")]

        public IEnumerable<string> GetC()

        {

            return new string[] { "B1", "B2" };

        }

        // GET api/values/5

        public string Get(int id)

        {

            return "value";

        }

        // POST api/values

        public void Post([FromBody]string value)

        {

        } 

        // PUT api/values/5

        public void Put(int id, [FromBody]string value)

        {

        } 

        // DELETE api/values/5

        public void Delete(int id)

        {

        }

    }

}

The output comes like below:

Convention-based Routing:

In the convention-based routing, Web API uses route templates to determine which controller and action method to execute. At least one route template must be added into route table in order to handle various HTTP requests.

Now we define convention based routing in ValueController.cs page like below:

public IEnumerable<string> GetD(string name, string Designation)

{

      return new string[] { "B1", "B2" };

 }

when you run the application output show like below:

When u click the EmployeeInfoDetails it will show one window like

when you pass the parameters in convention-based routing it's display the querystring.

if we don't want to display querystring, then we go for attribute based routing.