Create First Web API Hello World application with repository pattern

In this I am going to explain how to create First Web API Hello World application with repository pattern.

In previous article I have explained Introduction to ASP.NET Web API.

I am using Visual studio 2019 and .net framework to create this application.

Implementation:

STEP 1 : Open VS 2019. Click on create a new project and select ASP.Net web application (.Net Framework).

STEP 2 : Configure new project window will be open. Enter the project Name, select location and click on Create button.

STEP 3 : Create a new ASP.NET Web application window will be open. Select Empty and check the Web API from add folders & core reference. If you want to create MVC + Web API, then select the MVC option.

Application will be created and looks as below attached screenshot.

Firstly, you need to check the important files of Web API application WebApiConfig.cs and Global.asax

WebApiConfig.cs

This file is very important because it configure the routes of incoming request. This file is located under App_Start folder and looks as shown below:

public static class WebApiConfig

    {

        public static void Register(HttpConfiguration config)

        {

            // Web API configuration and services

            // Web API routes

                 config.Routes.MapHttpRoute(

                name: "DefaultApi",

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

                defaults: new { id = RouteParameter.Optional }

            );

        }

    }

Global.asax

This file has Application_Start method. This method is executed when application starts for first time. As you see Web API routes are configured in this method. If you check the definition of this, will redirect you to WebApiConfig.cs file.

protected void Application_Start()

        {

            GlobalConfiguration.Configure(WebApiConfig.Register);

        }

STEP 4: Add an interface to project

Firstly, we need to create a folder for interface. Right click on project name >> Select add >> select the new folder.  Rename the folder name. I have named it as Interface.

Now right click on interface folder and select class. Select the interface from given options. I have named it as IHello.cs

Complete code of Interface (Ihello.cs)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using WEBAPI.Models;

namespace WEBAPI.Interface

{

    public interface IHello

    {

        string HelloMethod();

    }

}

STEP 5: Add service to project

Similarly, to interface add a folder to project and named its as Service. Right click on Service folder and select class.  Select the class from given options.

Complete code of Service (HelloService.cs)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using WEBAPI.Interface;

using WEBAPI.Models;

namespace WEBAPI.Services

{

    public class HelloService : IHello

    {

        public string HelloMethod()

        {

            return "First Web API Hello World application with repository pattern";

        }

    }

}

STEP 6 : Add controller

Now let move to next step. Add controller to project. Right click on Controllers folder >> Add >> select Controller. Select Web API 2 Controller-Empty, click on add button and enter controller name.

STEP 7: Add Method

Create a method. I have created a method (HelloMethod) and return the first application text.

Complete code of Controller (HelloController.cs)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Net;

using System.Net.Http;

using System.Web.Http;

using WEBAPI.Models;

using WEBAPI.Interface;

namespace WEBAPI.Controllers

{

    public class HelloController : ApiController

    {

        private IHello _hello;

        public HelloController(IHello hello)

            {

            _hello = hello;

            }

        [HttpGet]

        public string HelloApplication ()

        {

            return _hello.HelloMethod();

        }

    }

}

STEP 8 : Enable dependency injection using Unity

To enable the dependency injection in this project I am using Unity Container. Install the Unity Webapi using NuGet package.

install-package unity.webapi

This will create a class (UnityConfig.cs) in App_Start folder. Open this file and map the interface and class dependencies. Means need to register the created service class to Interface.

container.RegisterType<IHello, HelloService>();

Complete code of UnityConfig.cs

using System.Web.Http;

using Unity;

using Unity.WebApi;

using WEBAPI.Interface;

using WEBAPI.Services;

namespace WEBAPI

{

    public static class UnityConfig

    {

        public static void RegisterComponents()

        {

                                    var container = new UnityContainer();

            // register all your components with the container here

            // it is NOT necessary to register your controllers

            // e.g. container.RegisterType<ITestService, TestService>();

            container.RegisterType<IHello, HelloService>();

  

            GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);

        }

    }

}

STEP 9: Now we need to add the Unity Registercomponents in Application_Start method of Global.asax file.

Complete code of Global.asax

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.Http;

using System.Web.Routing;

namespace WEBAPI

{

    public class WebApiApplication : System.Web.HttpApplication

    {

        protected void Application_Start()

        {

            UnityConfig.RegisterComponents();

            GlobalConfiguration.Configure(WebApiConfig.Register);

        }

    }

}

  

All done, now run the application. Type the URL according to WebApiConfig.cs file like Api/controller/Action/id e.g. https://localhost:44373/api/hello