Implementation of Dependency Injection in Web API

Introduction

In this article, I will show you a simple implementation of Dependency Injection in the Web API. Here we create an application that implements Dependency Injection.

Step 1

Create a Web API application.

• Start Visual Studio 2012.
• From the start window Select "Installed" -> "Visual C#" -> "Web".
• Select "ASP.NET MVC4 Web Application" and click on the "Ok" button.
  
  
  
  
• From the "MVC4 Project" window select "Web API".
  
  
  
  
• Click on the "OK" button.

Step 2

Create Two Model classes first is "ResponseModel" and another as "ResultModel".

• In the "Solution Explorer".
• Right-click on the Model Folder.
• Select "Add" -> "Class".
• Select "Installed" -> "Visual C#" and select "Class".
  
  

Add the following code in the "ResponseModel.cs".

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace DepeninjecAPI.Models
{
    public class ResponseModel
    {
        public int ID { get; set; }
        public DateTime Date { get; set; }
    }
}

 

Add the following code in "ResultModel.cs" class.

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace DepeninjecAPI.Models
{
    public class ResultModel<T>
    {
        public int Full_count { get; set; }
        public int Pagecount { get; set; }
        public IEnumerable<T> Rslt { get; set; }
    }
}

 

Step 3

Add a new Folder to the project.

• In the "Solution Explorer".
• Right-click on the Project.
• Select "Add" -> "New Folder"and change the name of it to "Collect".
  
  
  Add a new interface in this folder.

• Right-click on the "Collect" folder.
• Select "Add" -> "New Items".
• Select "installed" -> "Visual C#" and select "Interface".
  
  

Add the following code in this interface:

using DepeninjecAPI.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace DepeninjecAPI.Collect
{
    public interface IRedingCollect
    {
        void Save(ResponseModel read);
        ResultModel<ResponseModel> Get();
        ResultModel<ResponseModel> Get(int No_page);
    }
    public class ReadingCollect :IRedingCollect
    {
        private readonly IList<ResponseModel> intercollect = new List<ResponseModel>();
        public const int PageSize = 5;
        public void Save(ResponseModel read)
        {
            intercollect.Add(new ResponseModel { ID = read.ID, Date = read.Date });

        }
        public ResultModel<ResponseModel> Get()
        {
          return this.Get(1);
        }
        public ResultModel<ResponseModel> Get(int No_page)
        {
            var Gap_No = (No_page - 1) * PageSize;
            return new ResultModel<ResponseModel>
            {
                Full_count = intercollect.Count(),
                Pagecount = No_page,
                Rslt = intercollect.Skip(Gap_No).Take(PageSize)
            };
        }
    }
}

Step 4

Create a Controller "ResponseController".

• In the "Solution Explorer".
• Right-click on the Controller folder.
• Select "Add" -> "Controller".
  
  
  
  
• Click on the "Add" button.

Add the following code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using DepeninjecAPI.Models;
using DepeninjecAPI.Collect;
namespace DepeninjecAPI.Controllers
{
    public class ResponseController : ApiController;'
    {
        private readonly IRedingCollect collect;
        public ResponseController(IRedingCollect col)
        {
            collect = col;
        }
        public void Post(ResponseModel read)
        {
            if(read==null) throw new HttpResponseException(HttpStatusCode.BadRequest);
            collect.Save(read);
        }
        public ResultModel<ResponseModel> Get()
        {
            return Get(1);
        }
        public ResultModel<ResponseModel> Get(int No_page)
        {
            return collect.Get(No_page);
        }
    }
}

Step 5

Now we add a class in the "App_start" folder:

• In the "Solution Explorer"

• Right-click on the "App_Start" folder.

• Select "Add" -> "Class".

Add the following code:

 

using DepeninjecAPI.Collect;
using DepeninjecAPI.Controllers;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Http.Dependencies;
namespace DepeninjecAPI.App_Start
{
    public class SolveController:IDependencyResolver
    {
        private static readonly IRedingCollect readcollect = new ReadingCollect();
        public object GetService(Type type)
        {
            return type == typeof(ResponseController) ? new ResponseController(readcollect) : null;
        }
        public IEnumerable<object> GetServices(Type type)
        {
            return new List<object>();
        }
        public IDependencyScope BeginScope()
        {
           return this;
        }
        public void Dispose()
        {
        }
    }
}

 

In the "WebApi.config" file add the following line of code:

config.DependencyResolver = new SolveController(); 

Step 6

Execute the application and change the URL to "http://localhost:43200/api/Response".Then the output will be as in the following: