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:

Output