Building Your First Application in aspnet Web API

In this tutorial, you will learn what is Asp.Net Web API and Why do we use it. Here I will also show you how to create your first Web API service with Visual studio 2015.

What is Web API?

Asp.Net Web API is a powerful platform for building HTTP enabled service APIs that expose service and data. It can be consumed by a broad range of clients including browsers, mobiles, desktop and tablets. As it is HTTP service, so it can reach a broad range of client.

Asp.Net Web API is very much similar to Asp.Net MVC because of it contain the Asp.Net MVC feature like routing, controllers, action results, filter, model etc. Note Asp.Net Web API is not a part of MVC framework. It is a part of the core Asp.Net. You can use Web API with Asp.Net MVC or any other types of web application. You can also create a stand-alone service using the Web API.

Note:  Using ASP.NET Web API we can only create HTTP services which are non-SOAP based.

Why do we need Web API?

As you know, today we all are connected with internet. Only web based application is not enough to reach to everyone. Now a day, we all are using apps through mobile devices, tablets which makes our life easy. So, if you want to expose your service to everyone which is accessible on browser as well as modern devices [Mobiles and Tablets Apps] and run fast than you need to expose your service as API which is compatible with every browser as well as these modern devices.

Asp.Net Web API uses the full features of HTTP like request/response headers, caching, versioning etc. It is also a great platform where you can create your REST-FUL Services. You don’t need to define extra configuration setting for different-different devices unlike WCF REST Services.

Note: I want to clear one misconception that Web API does not replace to WCF. WCF is still a powerful programming model for creating SOAP based services which supports a variety of transport protocols like HTTP, TCP, Named Pipes or MSMQ etc. 

Start with First Web API Project

Open Visual Studio (I am using Visual studio 2015) and from the File menu, select New and then click on the Project. It will open a New Project window.

I am using C#, so from the Installed Templates, choose the Visual C# node and under Visual C#, select Web. In the list of project templates, choose ASP.NET Web Application. Give the name the project "WebApiSampleProject" and click OK. It will open a New Asp.Net Project dialog where you can select many type of template for the project.

In the New ASP.NET Project dialog, select the Empty template and check Web API. Click OK.

So, finally you have created a Web API project. It will create a default structure for the project

Add a model class

Model represents the data. It is an object of your data. The model contains all application logic such as business logic, validation logic, data access logic etc. Web API can automatically serialize the model data to JSON, XML or some other format. The serialize data write into the body of HTTP response message. Client can access the data after de-serialization.

To add new model class, in the Solution Explorer, right click on the Models, select Add and Class. 

It will open a dialog for Add New Item, select Visual C# node and select Class and give the proper name “Employee” for the model class and select Add. Modify the code for the model as below.

namespace WebApiSampleProject.Models
{
    public class Employee
    {
        public int EmployeeId { get; set; }
        public string EmployeeName { get; set; }
        public string Address { get; set; }
        public string Department { get; set; }
    }
}

Add a controller

Web API Controller is responsible for handing all HTTP requests which can be come from browser, mobile device, desktop web application or any other.

In Solution Explorer, right click the Controllers folder and select Add and then select controller. 

Note: Web API controller inherit the ApiController class instead of the Controller class.

It will open Add Scaffold dialog, select the Web API Controller – Empty template and click on Add. 

In the Add Controller dialog, give the proper name the controller "EmployeeController" and Click on Add.

You will see scaffolding creates an “EmployeeController.cs” class inside the controller folder.

Add two methods in the controller “GetAllEmployees” and “GetEmployeeDetails” and make dummy data for the Employee. See the below code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using WebApiSampleProject.Models;

namespace WebApiSampleProject.Controllers
{
    public class EmployeeController : ApiController
    {
        IList<Employee> employees = new List<Employee>()
        {
            new Employee() { EmployeeId=1, EmployeeName="Mukesh Kumar", Address="New Delhi", Department= "IT" },
            new Employee() { EmployeeId=2, EmployeeName="Banky Chamber", Address="London", Department= "HR" },
            new Employee() { EmployeeId=3, EmployeeName="Rahul Rathor", Address="Laxmi Nagar", Department= "IT" },
            new Employee() { EmployeeId=4, EmployeeName="YaduVeer Singh", Address="Goa", Department= "Sales" },
            new Employee() { EmployeeId=5, EmployeeName="Manish Sharma", Address="New Delhi", Department= "HR" },
        };
        
        public IList<Employee> GetAllEmployees()
        {
            //Return list of all employees
            return employees;
        }

        
        public Employee GetEmployeeDetails(int id)
        {
            //Return a single employee detail
            var employee = employees.FirstOrDefault(e => e.EmployeeId == id);
            if (employee == null)
            {
                throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotFound));
            }
            return employee;
        }
    }
}

In the above controller you can see that the method “GetAllEmployees” return the list of all employees and the method “GetEmployeeDetails” returns the detail of single employee. See the below chart which shows how controller use route URL to perform action.

Run the Web API

To see the result, you can just create a client application which will use this web api or you can just simply press F5 or Ctrl+F5. It will open the browser with Url like http://localhost:53037/

To get all employees list, you need to make changes in the Url such as http://localhost:53037/api/employee.

To get the details of single, you need to pass the employee id in the Url http://localhost:53037/api/employee/4

Conclusion:

So, today you learn what is Web API and why you can use it. You alos learn how to create your first application in Web API.

I hope this post will help you. Please put your feedback using comment which helps me to improve myself for next post. If you have any doubts please ask your doubts or query in the comment section and if you like this post, please share it with your friends. Thanks