Dependency Injection in .Net with example using Ninject

Reducing the dependency between two or more classes by creating an Interface to its respective classes and making loosely coupled architecture, this is called Inversion of Control.  Here objects are created at run-time.

There are some IOCs in market for .net: Ninject, Unity, Autofac etc

Dependency injection will assign respective objects automatically.

There are Constructor Injection Property Injection, Method injection etc. Commonly used real-time injection is constructor injection.

Below is the example for dependency injection:


Open visual studio. Create new project [ I have selected Console application]

Go to Tools  ->  NuGet Package Manager Console



In package manager console, type: Install-Package Ninject

Internet connection is mandatory to install the package; else you can manually add reference of Ninject downloaded DLL.



Now we can view the Ninject.dll in our solution reference.
Create an Interface as below.



Below is the code for interface:

using System;

namespace DependencyInjectionExample
{
    public interface IStaff
    {
        string getStaffDetails();
    }
}

Screenshot:


Create class file where we need to define the function.

Created a class as ‘TechnicalStaff’ and inherits the interface ‘IStaff’ as below:


using System;

namespace DependencyInjectionExample
{
    public class TechnicalStaff : IStaff
    {
        public string getStaffDetails()
        {
            return "19 Technical staff";
        }
    }
}

Screenshot:



Create a new class as Employee as sown below:




Place the below code in the employee class.


using System;

namespace DependencyInjectionExample
{
    public class Employee
    {
        private readonly IStaff staf;

        public Employee(IStaff staffing) //creating contructor
        {
            staf = staffing;    //Inversion of control
        }

        public string Getdetails()
        {
            return staf.getStaffDetails();
        }
    }
}


screenshot:



Now coming into program.cs file, we need to add namespaces of Ninject.

using Ninject;
using Ninject.Modules;

Below is the complete code for Program.cs:

using System;
using System.Text;
using Ninject;
using Ninject.Modules;
using System.Reflection;

namespace DependencyInjectionExample
{
    class Program
    {
        static void Main(string[] args)
        {
            var kernel = new StandardKernel();
            kernel.Load(Assembly.GetExecutingAssembly());
            var details = kernel.Get<IStaff>();

            var employee = new Employee(details);
            string result = employee.Getdetails();

            Console.WriteLine(result);
            Console.ReadKey();           
        }
    }
    public class DependInj : NinjectModule
    {
        public override void Load()
        {
            Bind<IStaff>().To<TechnicalStaff>();
        }
    }

}



In the above code, we can see that TechnicalStaff.cs and Employee.cs doesn’t have any direct communication. Interface plays a key role. Sending the interface as a parameter for constructor defines the Inversion of Control.


OUTPUT :