What is dependency injection in .NET

Naresh Beniwal

4y1.1k.NET

6 Replies

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Sachin Singh4y ago
Accepted answer
Actually, to achieve Dipendency Inversion principal (D of Solid) software engineers follows multiple methods, like factory pattern etc but the Dependency Injection is the favorite of all.
Now think it like this
public Class Employee
{

public Void AddEmployee(Employee emp)
{
   try{
   // add to DB
}
catch (Exception ex)
{
  FileErrorHandler errHandler= new FileErrorHandler();
  errHandler.HandleError(ex.Message.ToString());
}
}


}

public class FileErrorHandler
{
  public void HandleError(string Message)
{
   System.IO.File.WritleAllText(@"D://errorFolder/FileError.txt"Message);
}
}
In the above code everything is fine, but there is a blunder if you think correctly.
Employee class is actually dependent on FileHandler class, as Employee class is creating the object of FileHandler. Meaning, are tightly coupled.
Later if the demand comes to write error on DB table and not on File then you will have to modify the Employee class, Build it and retest everything which will increase the Software Cost unnecessarily (You will have to pay the employee for this un-necessary task).

For this reason , we invert the task of Object Creation (Dependency Inversion Principal) by giving the preference of creating task to a third class (Like Unity container in old .NET or DI container in .NET Core) . This is usually achieved by DI, using Constructor.
public Interface IErrorHandler
{
public void HandleError(string Message);

}

public Class FileErrorHandler:IErrorHandler
{

public void HandleError(string Message)
{
// write error to file
}
}

public Class DBErrorHandler:IErrorHandler
{

public void HandleError(string Message)
{
// write error to DB
}
}

public Class Employee
{
private readonly IErrorHandler _errhandler;
  public Employee (IErrorHandler errhandler)
{
_errhandler=errhandler;
}
public Void AddEmployee(Employee emp)
{
   try{
   // add to DB
}
catch (Exception ex)
{

  _errHandler.HandleError(ex.Message.ToString());
}
}


}
Now you can see, at run time the interface IErrorHandler can be pointed to any of its child using DI Container in .NET Core or Unity Container or any DI framework available in market.And Employee class is now lossely coupled with ErrorHandler class.
Amit Mohanty4y ago
Dependency injection is a technique of passing the dependencies (other objects) to the class as constructor parameters, rather than allowing the class to create its own dependencies. It’s a technique used to reduce the necessity of creating objects inside the class and minimize tight coupling.

There are three types of Dependency injection:
1- Constructor Injection
2- Property Injection
3- Method Injection

Dependency injection has the following benefits:
1- Enables clean code
2- Enables unit testing
3- Encourages decoupling
4- Improves code maintainability
5- Centralizes code configuration
Pushpendra Shukla4y ago
The term dependency means to depend on anyone else which means if an object is dependent on other objects that are called a dependency. Dependency is a relationship between a component or class that can be thought of as a uses relationship generally the parameterized constructor that provides an object for a needed class. If you have more than one class that class is dependent on each other that is dependency. The dependency is injected into a parameterized constructor.

Read the complete article in dependency injection.

https://www.c-sharpcorner.com/article/complete-signup-login-system-using-dependency/
Vishal Joshi4y ago
Dependency Injection (DI) is a design pattern supported in every language not only in .net.
with the help of the OOPS concept, we can manually achieve it in our software development.

In .net core, it gives a built-in facility for dependency injection so no need to manually write extra code.

Also, you can review the below link for detail and example:
https://www.dotnettricks.com/learn/dependencyinjection/implementation-of-dependency-injection-pattern-in-csharp
https://www.c-sharpcorner.com/UploadFile/85ed7a/dependency-injection-in-C-Sharp/
https://www.c-sharpcorner.com/UploadFile/damubetha/solid-principles-in-C-Sharp/
Vishal Yelve4y ago
Dependency Injection (DI) is a software design pattern that allows us to develop loosely coupled code. DI is a great way to reduce tight coupling between software components. DI also enables us to better manage future changes and other complexity in our software. The purpose of DI is to make code maintainable.

Please refer below article
https://www.c-sharpcorner.com/UploadFile/cda5ba/dependency-injection-di-and-inversion-of-control-ioc/
Rajanikant Hawaldar4y ago
https://www.c-sharpcorner.com/UploadFile/85ed7a/dependency-injection-in-C-Sharp/